Mother absolutely livid after i shaved my legs, but she refuses to fully explain why?

so i (15m) have always hated my hairy legs so one day when my sister came to visit this summer i asked her some tips on shaving my legs and she lended me her razor, so i shave and just kinda go on about my day, i knew my mom wouldnt exactly be enthusiastic about it but i didnt expect her to get so angry. So i was gonna go cycling with my mother when she notices my legs and goes "You shaved your legs?" I said "Yeah" casually, then asked her if she was ready. She puts her hands in her hair turns away and goes "Are you stupid? They're gonna grow way thicker now." I tried saying "But i heard that's not true at all-" And she just cuts me off and storms out the house, and thats about all i saw from her, she turned off her location on her phone, deleted the location app and everything, refused to answer any calls from me or my worried father. After she came home we didn't say anything to eachother, so a day goes by and we talk a bit casually, i ask her if she s making anything for dinner, and she says yeah, seemed pretty normal, day goes by normally. Then yesterday we had dinner and when i went back to my room to go clean she just randomly comes in and goes "Did your sister help you in shaving?" and annoyed, i say "This again? I shaved them by my own accord beacuse i didn't like them." She scoffs and goes "Don't think just beacuse we're talking again i'm over it." and i respond with "Whatever, ma." And she goes out my room. Then when my sister comes home they start arguing i don't fully know what beacuse i geniuely couldn't bear to listen but she kept talking about her authority as the mother and some other stuff. Today i learned that the day she stormed out she went to my aunt's place absolutely livid and angry, my aunt and my uncle said they had never seen her so angry and she sounded on the edge of tears, so now i am absolutely confused, why would someone get so angry over someone shaving their legs? I really don't get it, it's my body i should choose, atleast in my opinion.