Frustrated

I have two children from previous relationships and am pregnant now with my bf baby. His mom won't let it go that this is my last pregnancy because this is her first and probably only grandchild by blood. It's really irritating I am excited to have one more but I also would have been just fine with the two I have. I feel like she should be happy and let it go.... Is that wrong? She also has my kids call her grandma but then says stuff in front of them like I'm finally a grandma which also makes me upset. I had to say something somewhere because I can't say anything to my bf about his mom....oh she's just excited is always there excuse for her behavior