BC_Mom

Don't be so hard on yourself. Maybe you could talk with the staff to see if they have a better understanding of her personality. She just may have ended up in the shelter because she was so nice and friendly (and not what the original owner was looking for). I know many pits have a bad reputation, but I hear far more of the stories of the sweet and loving ones.
God bless you for being a volunteer. Whatever you can do for whatever dog is more than I and many others are doing. Please keep going back and do what you can and what you feel comfortable doing. With a little experience under your belt, you will feel more confident too.