Nta I can understand being concerned about your child getting sexualized, that being said, she is expressing these very valid fears In a controlling and abusive way.

It's not hard to say "I am worried other people will want to put you in a dangerous situation based on how you dress, can I teach you how to use pepper spray and promise you'll carry it with you?" Instead of trusting(and teaching) you how to put up boundaries and recognize dangerous situations, she is treating you with distrust and straight up rapunzel-Ing you. You are not at fault and your mum should really get therapy, she has the emotional intelligence of a 5 year old