MIL being awful

Recently my MIL has been make rude back handed comments towards me bc I don't want her in the room while I deliver. It's nothing new since I told everyone even with my first I only wanted my Husband in the room. Normally when she does this I smile and act like I'm not offended or hurt by the things she says. Anyway we went to visit so my husband could work on refinishing our dinning room table, so I was inside alone with her, my one year old, and my grandmother in law. I started noticing that she was yelling at my son for little things. For example he likes to bring people toys and he tried bringing her several toys and when she wouldn't take them he sat them down next to her. Apparently she didn't like have the toys next to her on the couch and yelled "Asher come get this shit. Stop making a fucking mess kid." When he didn't immediately come get the toys she yanked him by the arm and smacked his hand and told him to listen to her. I literally saw red. He's a year old. Why on earth are you expecting him to jump up and know what your asking immediately. And why would you cuss a one year old that way. I try to step lightly since she's a recovering pill head and got out of prison a year ago and my husband wants to have a relationship with her. But lately she's been awful to me and my son. And I don't know why. I try to include her and let her be involved but I hold firm to my beliefs and what I want with my babies and deliveries. I guess I just needed to rant. Maybe I'm just overreacting with the pregnancy hormones.