I don't really get why you want to follow these people on instragram, but its not my business.
My wife does this kind of thing and it's annoying. I don't have an instagram, but I'll like say hi to the girl who grew up next to me and she want to play 20 questions for the next three days. In my wife's case it's driven by extreme jealousy from her father cheating on her mother.
I don't know your girl's underlying reason (feminism, jealousy, insecurity are possible reasons) but she is unlikely change. Figure out if you can deal (give up following girls or be in constant battle over it) or not and respond accordingly.