Does she know that her comments about your thinning hair bother you? Maybe the reason she said it all the time was that she never saw or understood that it bothered you, at least not as serious as it is. The thing is about your mustache comment is your intention. You said it to get back at her, to pinch her a little. While her comments which is undeniably not great either might not be coming from the same place. Yes, maybe she has that narrow minded idea that men have thicker skin, but then that's where you get in and educate her.

A negative plus a negative is not equal a positive. For you to change a negative number to a positive one is to added with a bigger number that's positive. If she's not that number, then let it be you. Yes it's unfair, but sometimes that's the price we pay for love and our loved ones.