I feel for you. That is why I keep saying that I can't foster because I know that I could not and would not trust anyone else.
Maybe if you had this person call you so you could give them all the info about Avon. You could get a feel for the home and you could always tell them later that you changed your mind and realized you couldn't give her up now. I think I would want to talk to them personally instead of just seeing words on paper. You might even be able to stay in contact with them and keep up with how she is doing.
Good Luck in whatever you decide to do.