Quite simple, get another bird in another cage and set it beside hers. this way she can get used to him/her. after a while start having them out together but always keep an eye on them so nothing bad happens, eventually you should notice her calm down and eventually become friendlier with the other bird and than start communicating with her companion when your away, eventually if they like each other enough you can transfer them into a larger cage together.

As for the reason she is screeching is she has had too much interaction with humans and now prefers to be around them at all time.



Hope this is of some use. and im sure others have other solutions to your problem.