My mother in law isn't respecting my parenting choices: Advice?

I’ve been with my boyfriend for three years. We have two kids, one I came into the relationship with. He took on the dad role & completely rock it! We had one of our own we were so excited because we both wanted a boy. We Never had an issue with his family, including his mom, but since I had my son, everything just switches up… I had his mom around the majority of my pregnancy and planned to have her here when we came home with the new addition. I just had some ground rules I expected everyone to follow, INCLUDING my family I said no kissing in the face. His body is okay (on top of his clothes). His mom completely ignores what I say and keeps kissing him, I keep reminding her, telling her I feel like you disrespect me, and it’s a slap in my face because my family not allowed to kiss him at all. She says she understands but KEEPS DOING IT!! I feel like a total b*ch to keep reminding her, as I can tell it bothers her. I tell my boyfriend he says he going to tell her something and he does it just keeps happening. Im just so frustrated and over it at this point idk what to do.