One of the very first things I do after qualifying a sponsee is to let them know that it is thier program, not mine, I will take them through the steps as quickly as they wish or as slowly as they wish.
I have not fired a sponsee yet, I kind of got fired by my first sponsee....... he was honest which I like, he told me he no longer had time to make the one meeting a week he was coming to and did not have the time to work the steps with me. He thanked me for being his sponsor...... I let him know AA and I would be there for him if he ever felt the need and thanked him.
Unless I had a sponsee lie to me or not keep commitments I would not fire one, I would let them drift off into the sunset, if they find another sponsor, that is fine, if they don't I will be there for them when they are ready.
I have not had a sponsee I felt any need to fire, but Rowan I know that sometimes getting fired is good for some sponsees, so what you did was right for you and her, if I was in your shoes I may have done the same thing. You did not do anything wrong.