***So, Sierra bites you...You immediately say "No Bites!", that's it, that's ALL you say, and then you immediately put Sierra right down on the floor, no matter where you're at in the house you put her right down on the floor, and then you and EVERYONE ELSE WHO IS IN THE ROOM immediately turns their backs to Sierra. Literally you all turn your backs to Sierra...What you've just done is #1) You've put the bird in the place/position they dislike the most, on the floor, so that they are the lowest thing in the room and they lose all sense of dominance immediately; and #2) By literally turning your backs to the bird, you are physically and visually "shunning" the bird, and taking away the one thing that the bird loves more than anything in the world: the attention and acknowledgement of their "Flock". When I say that you and everyone else in the room must "turn their backs to Sierra", I mean it...Literally turn your backs to her...So now Sierra has lost all sense of dominance/control by being the lowest thing in the room, and she's also been "shunned" by her entire Flock. This period of "shunning" where everyone has their backs turned to Sierra MUST LAST FOR 5 MINUTES TO BE EFFECTIVE! If the "shunning-period" lasts any less than 5 minutes it won't have the effect necessary to mean anything to Sierra, and if the shunning-period lasts any longer than 5 minutes then Sierra will lose interest. So a 5-minutes shunning-period works very, very well.
Now what do you do during the 5-minute shunning-period? Well, what you don't do is say a single word to Sierra or about Sierra. You and everyone else in the room need to make it like Sierra doesn't exist and never did exist. So it's extremely important that you totally ignore anything and everything that Sierra says or does during the 5-minute shunning-period. You cannot acknowledge that Sierra is in the room at all. Sierra is going to do things like talking to you, screaming at you, etc., but you cannot say a word or make a single sound. You and everyone else in the room must be absolutely silent...Sierra is also going to do things like walk around you so that she's facing you, climb up your leg, fly to your shoulder, fly to her cage or a perch/stand, etc. So here's how you handle all of these things, basically there is one rule to follow: If Sierra leaves the floor, she must be put back on the floor, but SILENTLY! So if Sierra walks around you so that she's facing you, you simply turn your back to her again without saying anything or making a peep, and the others in the house do the same thing, they must always turn their bodies so that their backs are to Sierra. If Sierra starts to climb up your leg from the floor or she flies to your shoulder or she does this to anyone at all, all you do is SILENTLY, DON'T MAKE A PEEP WHILE DOING THIS, quickly put Sierra right back down on the floor again without making a sound, and then again turn your backs to her. If Sierra flies to her cage-top or onto a piece of furniture, etc., anytime she leaves the floor at all, you SILENTLY walk to wherever she has gone, get her, and put her right back down onto the floor and turn your backs to her again....When Sierra flies onto her cage or starts climbing up your leg, etc., it's always going to be your first inclination to say something like "No Sierra!", but you don't EVER want to say a single word, because any word that you say is paying attention to Sierra, she gets what she wants, and she wins. So make sure that you and everyone else in your house thinks of the 5-minute "shunning-period" as being completely silent time, and a time when no human being present can make a peep or say a word. If you and everyone else remembers to never, ever say a word at all during the 5-minute shunning-period, then this will be very successful much more quickly than if you continually break the rule and keep saying things. So think of this like a game, where the human's goal is to keep Sierra on the floor and keep everyone's back to her face, and keep totally silent, all for the full 5-minutes, and you win...If someone says anything to Sierra, if Sierra leaves the floor and no one silently goes and gets her and puts her right back onto the floor, or if anyone fails to keep their back to Sierra the entire time, then Sierra wins...Also, the way that I've found to handle a particular situation the best, is if Sierra ever flies-off to another room, no one make a sound, everyone stays silent, but one person silently goes to the room Sierra has flown to, gets her, silently walks with her back into the room where the "shunning-method" was started, and they put Sierra right back down on the floor and turn their backs to her again. I've found that if you keep the bird on the floor in the same room you started the "shunning-method" in and you don't just go to a different room that the bird may fly to and put them on the floor in that room for the rest of the 5-minutes, it's much more effective. I think this is because by continually putting the bird right back onto the floor in the room where the "shunning-method" was started that this is making the point to the bird that they have zero dominance in this situation, and they are not going to be allowed to make ANY CHOICES at all, including flying to a different room...And most-importantly, STAY SILENT THE ENTIRE TIME!!!
***Also, two other FYI's: #1) If you are sitting in a room with Sierra and there are other people in the room sitting down, and Sierra bites you or any of them, EVERYONE WHO IS IN THE ROOM must immediately stand-up and turn their backs to Sierra, even if they weren't the one who was bitten. You can't have one person who remains seated and facing Sierra. That won't work, as Sierra needs to know/see that her ENTIRE FLOCK is "shunning" her....and very important #2) If Sierra bites you, you do the Shunning-Method once, and then Sierra bites you immediately again after the 5-minutes is up, then you must do the whole thing over again for it to be effective!!! So if this happens you once again say "No Bites!", put Sierra on the floor, and turn your back to her. The first day you start using the Shunning-Method, you may very well do it a dozen times in a row, which is required for it to be effective and for Sierra to get the point. So while this can be very frustrating the first day, I've not ever seen any other method work as effectively and as quickly as the Shunning-Method, specifically with Conures because they value their attention/interaction and relationship/bond with their person/people and their flock so very much, and they also HATE being the lowest thing in the room.
***Another important tip is how you should handle it when the 5-minute shunning-period is up...You should ever just go and pick Sierra up or start talking to Sierra as soon as the 5 minutes is up. That tends to negate what you just did. Instead, everyone who is present just needs to not say anything at all to Sierra when the shunning-period is over, they just need to go back to what they were doing prior to the biting. Go and sit down on the couch or a chair, start talking to each other again BUT NOT TO SIERRA right away. She'll most likely be left standing in the middle of the floor by herself, which is good. LET SIERRA COME TO YOU AFTER THE SHUNNING-PERIOD IS OVER! And don't just start coddling her right away, let her come to you, let her climb up onto your lap or shoulder, and then silently just start petting her again, and then start talking to her normally. TREAT IT LIKE THE SHUNNING PERIOD NEVER HAPPENED. And if by chance she immediately bites you again, just say "No Bites!" again, everybody stands up, put Sierra on the floor, everyone turns their back to her again, and everyone is silent and keeping Sierra on the floor for another 5-minutes. And so on, until she stops biting you...And if she doesn't bite you for another 2 hours, then that's great, but the second she bites you or anyone else again, it's "No Bites!" and on the floor again for 5-minutes...While it can be frustrating the first day or two, I have seen this exact "Shunning-Method" stop a constantly biting pet parrot from biting anyone in a matter of one day and about 12 "shunning-periods" throughout that day. That's how effective this is with most hand-tamed, pet parrots. And it's also important that if Sierra stops biting completely but then a month later she bites someone, that you and everyone else immediately does the Shunning-Method again; it must be done every single time Sierra bites. She will slip-up from time to time after she initially learns not to bite, so it's on you and everyone else in your household to follow the rules every time Sierra does bite anyone. It works tremendously well when used consistently and done correctly.
***Something else that is extremely important that you need to address ASAP is Sierra's diet, as already mentioned above by a few other members...I don't believe that captive/pet birds who are on an all-seedmix diet are necessarily in a bad situation diet-wise, HOWEVER they need to be on a healthy, varied, low-fat seed-mix if a seed-mix is going to be their staple-food. And unfortunately Kaytee Fiesta and most-all Kaytee seed-mixes are full of fat, sugar, carbs, etc., and quite often result in the bird developing nutritional deficiencies, but more importantly and most-commonly the end-up developing Fatty Liver Disease and Kidney Disease very early in life, and they also usually die long before they should...