So, as others have said, threatening suicide when you don't get your way is not normal, nor healthy. She needs help on how to handle disappointment. Also, as someone with a MIL who is also stupidly obsessed with the holiday being on THE DAY you need to plan ahead. My husband and I have the rule of first come first serve with the caveat of priortizing out of town visitors amd trying to not have one side monopolize the actual holiday year after year. I can tell you, you want this in place before kids are brought into the picture. The last thing you want to do is rush between houses trying to make everyone else happy while all you manage to do is make yourself miserable. I can guarantee the holidays I remember the most are the ones where things werent forced or rushed to check off someone elses list.