The first thing I'm going to tell you is to absolutely NOT get her a mate...The best advice I can give you on this particular topic is "Never ever buy another bird for your first bird! Only buy another bird if you want one, and even then you cannot house them together or even let them out together necessarily, they must be housed separately and eased-into knowing each other...And even that may never work out...You have absolutely no guarantee that if you bring home another bird, no matter what species or gender, that they will get along at all, or that they won't be aggressive and hurt each other...They may simply just tolerate each other, or not at all. And then you have 2 birds that you're responsible for, even if you didn't want another one. So this is not the answer at all...Not to mention that you haven't trained her yet, you certainly don't need another bird right now, as your attention and free-time needs to be dedicated to her...
If she's around a year old then this could be hormonal, it probably is at least a bit hormonal..However, it doesn't sound like she was a hand-raised baby, or if she was a hand-raised baby, she had a period of time where she got no interaction with people at all...But more than likely, she is a parent-raised bird who was not put into a "Weaning Cage" while she was being weaned and fledging, and even though this sounds odd, she probably never learned to play with toys. This is extremely common with Cockatiels who are parent-raised and that were not raised inside of a Weaning-Cage with lots of different toys and such...So essentially, they really don't know how to play...and you have to show them!
It sounds like you just need to keep working on hand-taming her, and you also are going to have to show her how to play with her toys. Show her how much fun it is to play with them, show her what to do with them, etc. Because right now she has no idea what they are or what she is supposed to do with them...
And no, you don't want to just "grab her", if she is not stepping-up for you, then you need to start at the beginning of the hand-taming process. It often helps if you get them away from their cage, in a different room with the door shut. However, if you can't even get her to step-up for you or come out of her cage for you, then you need to hit the "reset" button, and start from step #1 of the hand-taming process, which is just sitting by her cage as close as you can get without her being angry about it, and reading to her, talking to her etc. And go from there...
3 months isn't long at all, it often can take 6 months to over a year to even get a non-tame parrot to simply step-up. It's a matter of patience on your part, as you must go at her pace, not your pace...
And her diet needs worked on big-time...Doritos are not a good treat at all and shouldn't be given, they are loaded with salt which can be very, very bad for them...It's a good idea to get her to a CAV for a wellness-exam, and then start phasing-out the all-seed diet and start incorporating a healthy pellet as her main staple, and only supplemented by a healthy, varied seed mix without any sunflower seeds. Only use treats like sunflower seeds, peanuts/nuts of any kind, etc. as training rewards and that's it. Do not just give them to her as a part of her diet, but rather only give them to her when she does something good for you, such as stepping-up, coming out of her cage, etc.
It's just going to take daily work and patience...
Also, do you have her cage located in the main room of your house where the people in your house spend most of their time when they are home? (Usually this is the living room, family room, den, etc.) Her cage should not be in another room where you are not at when you're home. Even if you're not directly paying attention to her, she is far more-likely to entertain herself inside of her cage with her toys if she's in the same room as you are, while you're watching TV, reading, playing video games, on the computer or your phone, etc., just having her cage in that room with help tremendously with her taming process (being around people), and with her behavior...A bird that can hear people in the house but can't see them is not a happy bird...