Is it just that she doesn't seem to be listening and learning about religion, or is she ignoring direct instructions or be disruptive? If the problem is that she's not interested in the subject matter I don't know that there's much you can do, except maybe wait and try again when she's little older. Kids with adhd tend to be less mature and often need more time, especially when dealing with abstract concepts (like religion).
I don't think it's all that uncommon for kids to need a connection with the adult before they'll really respond to them. I guess one solution might be to help out in the class so that the teacher (not you) can spend a little extra time with your daughter to build that connection.
Yesterday I was called on the phone by my 6 year old daughter's religion class teacher saying that she was having a hard time with my daughter. My daughter doesn't listen and she (the religion teacher) feels as if she is shutting down and building a wall. I was asked to drive to the class and stand next to my daughter to help.
My 6 year old daughter needs a strong sense of connection (be it warmth, attention, bond...) from other people (teachers, grown ups, relatives). If she doesn't then she will ignore that person, will not listen (well) and can shut down. Do you have that also with your child? What do you do?