Screeching cockatiel

Hi, I'm hoping someone will be able to help me, a week ago I was given a four or five year old cockatiel called Jennie. She's a lovely bird and I'm already feeling quite attached. The problem is she's usually quite quiet, she doesn't speak but whistles often which is a nice sound, but whenever the TV is put on, she screeches until it's turned off. When I spoke to the previous owner I was told this is something that she always does, and to keep the TV volume low. I've tried this and she screeches anyway, as well as not being able to hear the TV! I've taken to just not putting the TV on for the last few days but can't see this a being a solution. I've tried ignoring her when she does this so she knows she's getting no attention, incase she thinks I'm praising her if I speak. I've also tried covering the cage but she still screeches! The previous owner also had a cat so Jennie was not ever out of the cage and sometimes seems very timid and hisses when I put my hand in the cage to feed her, could this be she just needs more time to get used to me? I would love to think I could retrain her if this is possible, but I'm seven months pregnant and feel I may have taken on too much of a responsibility, even though I'm very reluctant to lose my little friend. Please someone offer advice!

Hi Auntie,
have 1 tiel so am no expert but can the bird see the tv while it is on or is it out of sight? What about moving the bird to another room while u watch tv? or perhaps letting her see the tv when it is on?
Perhaps Jennie will quit doing this after she is used to being at your house. There are a few good books out there for training birds.
Any one have any suggestions on books they have read on training that they liked.
At any rate this will bump the the thread up and hopefully someone with more tiel experience will chime in or someone who has used books or dvds for training can chime in on what they have liked or not liked.
let us know how you and Jennie are doing.