If she is new to her faith it can be confusing and she needs to study and find out the truth for her. I would suggest prayer and taking her problems to the source.

I have been a Christian my whole life and don't feel any conflict with my faith and wanting to have 24/7 D/s relationship. But, these are things that everyone has to work out for themselves. The Bible does tell us that if we feel in our heart that something is a sin then for us it is. She needs to understand what her feelings are where they are coming from.