Have issues with mother in law about gender thoughts?

Ok so I normally get this upset over things she said but this time I just can't seem to blow it off with my 2nd child & husbands 1st child she wasn't happy we were expecting this time she was even more so saying "your kidding right" until her son said "why can't you be happy for us if we are?" Witch this baby was a surprise to us as well. Anyways now anyone asks or she over hears them ask what we are having or what we think we are she automatically goes into a spill. " It's a boy she's never going to get a girl I didn't get a girl and she won't; we keep telling her it's going to be a boy." Witch goes on for a good 30min. Or more so. This is everytime and I've gotten to the point I just walk away before I lose it on her. I know this shouldn't be a big deal but since we told family & friends it's none stop. She has told me multiple times that she hopes I'm not as bad as she was when she found out she was having a boy she cried for weeks that he was a boy since she wanted a girl and was only allowed because of health reasons to have one baby. We have 2 boys one who just turned 10 and the other is 3 witch if this is a boy it will be loved just as much but I just feel this one's a girl. Totally different symptoms compared to the boys.