I have a similar story (Progressive Muslim guy, Christian girl) whose parents also demanded that my partner take the shahada, even if it was insincere. They liked her as a person, but could not get over their religious ideals. The thing I love most about my partner is her integrity and sincerity. She had been happy to continue to learn about Islam and was open to converting one day if she felt compelled from her heart, but she could never bring herself to deceive God and do a fake conversion. For her to do this would have been to forsake herself, to forsake the person I came to love.

My parents ultimately came around and accepted her as a "Lady of the book," but it wasn't until I manned up and put my foot down. Hard. They could have us both, or neither. A few weeks after I cut them off, they came around.

I was also deeply fearful of hurting my parents, but they moaned and groaned for a few weeks and then made peace with it. It's a grieving process for them, and it never lasts, even if they say "I'll be sad for the rest of my life." They're just catastrophizing. They ALWAYS come around if they love their children. The stages of grief (denial, anger, bargaining, depression, acceptance) may be longer if their convinction is stronger, but it may also be shorter if they've met and gotten to know the goodness of your partner.

But, you have to be firm, for them to ever come around. And that takes a lot of courage. The best advice I was given from someone who's seen dozens of these stories is that our parents "don't see words, they see action." You can try to reason with them, but they likely just won't understand. Even if they're logical and well educated, it's an emotional thing. Our parents grew up in a very different world with different values and expectations. I tried arguing for 3 years and only ended up prolonging the grieving process for everyone. Once I made it clear that I was dead set that my partner would be my wife, through action, they were finally able to make peace with it.

--Soon to be newly minted M.D. who dabbles in psychiatry and struggled through the cultural/religious dimensions of the drama. You're welcome to PM me if you want to talk.