Am I overreacting?

I'm transgender and I tried explaining to mum that I have a hard time because I can't wear my binder because of the fibromyalgia and she responded with that they cause kidney damage. I told her that wasn't the case and that even doctors say it's okay as long as you wear them properly.. she then said "well I identify as a skinny person but you don't see me squishing everything into place and causing damage"......... I actually feel like crying because I don't think she realises that she literally just made fun of me being trans... I don't know how to feel because she's been my number 1 supporter and now she goes and says this. Am I overreacting? I just feel really, really hurt. Especially because I've been having a really hard time dealing with not being able to take hormones because I'm on a waiting list...