Hats off to you!! The feeding you are doing is good; not too much at each given time so you don't overload her system.
Spend time with her without trying to put pressure on her. Let her take the initiative to make contact with you. Avoid making eye contact, face her sideways from a sitting/kneeling position, per her under the chin and keep movements slow, voices calm and reassuring. You can try hand feeding her once in a while. I once had a foster dog like that; she was an emaciated mess and so scared but after 6 months you wouldn't know it was the same dog.
I loved giving her a second life and I am sure you do too. She is lucky that you took her in. Hope they catch the jerks who did this to her.
If you decide to keep her, make sure you get her vet records in your name, county license etc. This will help in case her previous owners decide they want her back when they run into you. Also get a written statement from witnesses and the dates and location so you have proof of abandonment.
Enjoy her and keep us posted.
"If love could have saved you, you would have lived forever." RIP my awesome Wolfie Dog