Should I talk to my mum about this?

First off, I am on anon, which is horrible, I know. Secondly, My little sister (we were born about 10 years apart) is almost 14 now. She's always like wearing frilly dresses, and has one in particular right now that has no sleeves (it has straps on the shoulders). My mother has scolded her a couple of times while I was over about shaving her armpits if she wanted to wear that dress, because "no one wants to see your armpit hair". The school she goes to has a dress code that doesn't allow dresses, so she basically only wears these at home, and occasionally on any errands she might go on. The only one who seems to be bothered by this is my mother, and I feel like forcing a 14 yo to shave is unnecessary. I also don't know if it would be appropriate to talk to my mother about this as it's not my place to comment on her parenting, and I don't know if it would make my sister feel worse if I told her I thought our mother was being irrational. help?

Does your sister want to shave?

not specifically no, but she does because she enjoys wearing that dress