MIL problems-have no idea how to proceed

Sorry this is so long but could use advice.

So my MIL is very different from myself. I’m very calm and laid back, she freaks out about everything. I rarely yell and that is usually her first response to something she doesn’t like. Well the other night we went over for dinner, dinner was great. But after dinner both grandparents were playing with our 19month old. Our daughter right now is in a grandpa phase, he is her favorite right now. She changes pretty often and bounces around. But this upsets my MIL, she wants to be the favorite because she does more for her. So she was trying to get our daughter to come to her and our daughter was shaking her head no and hugging grandpa. It was kind of funny, I giggled a little on the inside cause it is cute. But grandpa giggled a little and grandma gets upset and starts yelling. She even went as far to tell her husband she is going to slit his throat while he sleeps. At this point my husband tells her that is enough, I am beyond shocked and don’t know what to do. So I’m sitting there while my husband is arguing with his mom about how that isn’t ok and she is playing victim saying you always side with him or she was just kidding. She then starts using how she helped me watch my daughter earlier in the day cause I got no sleep and am 36 weeks pregnant. So I took and nap and she watched her for 2-3 hours in the morning. She was pretty much like rubbing it in our faces that she helped and to be honest that upset me the most. I was like well I guess there is a price for her helping me, great. She gets to throw it in our faces whenever she wants. She is supposed to watch our daughter while I’m in labor but I’m at my wits end with her. She is usually pleasant. I can take her in doses. But now I don’t know if I even want to be around her. Don’t know if I’m over reacting or what. She hasn’t talked to us or apologized. What are y’all thoughts.