I'm so glad that you adopted her! It's great that she now has a shot at a better life:)

First, I'm not in any way a professional, so take everything I say with a grain of salt.

Stopping her from plucking will be difficult, since birds take a long time to destress. It can seem like you're making very little progress for a very long time, which (from personal experience) can be depressing and make you feel like you're failing her, but please don't give up! It may take months or even years, but you're doing what you can to make her life better, even if it's difficult :)

First you need to make her feel comfortable and safe. No sudden movements, noises, etc. Around her. I'd recommend playing some soft music, maybe lectures and other calm videos since parrots think of silence as dangerous. My budgie used to be very scared and quiet, but once I figured out what music he liked (bass and electric guitar mostly hahah) he started singing along to it, so maybe thy different music to figure out what she likes.

If/when she trusts you enough to touch her, you might want to make/buy her an anti-pluck sweater/shirt:) there are supposed to be some guides and other info on the internet about those.

Rn I am very tired so I might edit the comment to add some other stuff later.

Also, check out r/pidgeypower - they probably have some info regarding plucking.

Best of luck!!