I’m very glad that you are asking these questions before you get married. You’ve listed a number of issues that make it difficult for a couple to have a mutually satisfying and happy sex life. Your fiance has suffered a traumatic sexual assault. Religious teachings from an early age may have taught her that sex outside of marriage is morally wrong. On top of that, she is just plain tired.
It is a positive comment on your sensitivity and love that you are seeking answers instead of just being upset or blaming. That speaks well for your relationship. Since the two of you have such a difficult time talking about sex, I think you need some help. A counselor can provide a safe place and guidance so that you can work this through. Since you both have a Christian background, a Christian couples counselor might be a good choice.
I wish you well.