Ladies I need your help!

Briana

So I’ll give just a little back story first. My fiancé’s family is a little “different”. All of his siblings live with their mom and their significant others do also. He has a younger brother whose girlfriend isn’t necessarily my cup of tea. She’s barely legal but she gets under my skin. My fiancé and I don’t live with them, we actually live a few hours away. Well long story short, we came to visit them last week for the first time during this pregnancy and I was about 17 weeks but my belly is fairly large. Well the brothers girlfriend decides to rub it but then she proceeds to act like she is going to hit my belly. I let it go. Well we went to visit a week later and when we walk in she is making something in the kitchen. I walk past her to get to the back patio but then she stops me to look at my belly. She had a knife in her hand and acts like she is going to stab me in my belly. I didn’t say anything but I’m really at my breaking point with her and her actions and I’m afraid that my next reaction will be to immediately put my hands on her. What should I do? Should I talk to her about it or just wait and see if it happens again? HELP!