NTA thats so weird that she did that. First off shes never met you before and going through your bathroom drawers. You dont do that even to people you are friends with, short of maybe if the toilet paper roll is empty and you look for more or something extremely basic like that. Id be really upset about that.

Second, you didn't even get mad at her for snooping and using something that was yours, you just told her what it actually was. If it was me i would have also told her on the spot what it was and then silently congratulate myself for not yelling at her in front of everyone because i would be really mad about the violation of privacy, not "pulled her aside and expressed my concerns" so to not embarrass her.