I really need some advice on this

I need some advice. So almost every Sunday for the past 6 months I have been going to church with my boyfriend and his family. Well after church, my usual routine is to go to their house and spend the day with him and his family. No biggie, right? Well my mom has been getting really angry about it. She never says it outright but she has been showing signs of being jealous about the fact that I do this. Like tonight, after I got home my mom barged into my room to rudely ask me if she needed to stop cooking so much dinner on Sunday. She knows that I always eat dinner at their house on Sunday. I just don’t really get it. We never did anything on Sundays before and I’m with her the ENTIRE WEEK except Sunday. Any advice?