I think it's just a mother thing. That's what mothers are for, I guess...
I just read "I Am Not Myself These Days" by Josh Kilmer-Purcell, and there was the best line in there. Something like "My mom visted for three days and left, as that is the amount of time we can spend with each other before descending to a level of bickering that can only be known between two people who have shared one body."