I've thought long and hard about this, I come from a large family, and We all get along and fight in various degrees from time to time, Ive seen sibling become so tight they take vacations togeather and then because of a stupid comment not speak to one another for years. I would take her aside and ask her politely to keep her comments about your apperance to herself. Because of the nature,type and frequency of her comments I gaurentee she's spoiling for a fight. You do NOT need to offer any explantion you do not feel comfortable with. If she has any decency she'll back off, there is no need for her to pick like shes doing, and remember you also have the option to not addend family gatherings where she is in attendence. The comment about being a 'child fiddler' is uncalled for and should be delt with as soon as possible. Being transgended is NORMAL.