There are people here who know more about it than I do..they may have a different opinion...
I don't see anything here that would stand up as malpractice. I'm not sure there is even enough here to take to a licensing board.

Remember in legal cases..it's not so much about who is right or wrong...but it's about what you can prove...and how damaged you are. They won't consider only your word for it- regarding verbal agreements. She will have her own version of events, too.

Did you get any agreement in writing..that she signed?

Looks like you owe her. You plan on paying her, right?