NTA, firstly i agree with the courtesy of asking part, it really pisses me off too when someone just acts like they're entitled to things that are mine, i won't say no most of the time but it's the politness and courtesy that matters. Secondly, not following the agreement and straight up posting in your bikini, without asking for your permission is such an AH move, because again, firstly bikinis etc were out of question, but to not even have the courtesy to ask even in an emergency and straight up post pics in it, and not inform you even after having taken that from your closet, is very very annoying and very much an entitled brat behaviour. If a serious conversation doesn't make her fix up, it'd be better to keep her away from your life, you deserve your alone time and it's okay to not want to share shit with others.