It was in the heat of the moment, she surely didn't mean that, but that doesn't absolve her. Words from a parent hold high value to their child and something like this can really really hurt, especially if the child is so young. I remember after an excruciating argument with my sister my mother once said "it would have been better had I never had children" and I was there. I was already old enough to withstand that but god that shit stings right in the chest