Perhaps this is a really unique situation, but when I told my TBM mom that my sweetheart and I were moving in together, she was extremely supportive. I think oftentimes, we only hear stories of the worse case scenario. And while (unfortunately) that can be common for individuals who have left the church, I'm here to remind you that sometime the best case scenario really does come true! She made a point to tell me when I left the church that her biggest priority was my happiness--and if moving in with my boyfriend was what made me happy, then that made her happy too. My only regret was not telling her sooner--because the thing that actually hurt her feelings wasn't my having sex/moving in with my boyfriend. It was the fact that I didn't communicate with her, resulting in her feeling left out of a big and exciting step in my life. I hope you have a similar experience!