Just give her time. Sounds like she will need lots of it. You need to be patient. If she ever does that again, I would suggest just getting up and walking away. Don't try to convince her that you are not the bad guy.
Dogs that have been abused will behave that way for a long time and sometimes they never totally get over it. She will be fine with you in time.
She is a tiny little thing and the only way she knows to defend herself is with her teeth. Once she learns there is no reason to defend, I am sure she will be ok.