Am I overreacting?

I've spent months making flashcards for my year 12 mocks whilst my friend did no revision. This weekend (our exams are this week) she has been using my flashcards on quizlet (without telling me) that include detailed essay plans for sociology and my personal analysis of quotes for english lit. It's really annoyed me but I'm also scared I'm overreacting. I know I should have privated them but I didn't expect anyone to find them especially because I don't even tell people I use quizlet. I would have probably said yes if she had asked so I do feel like it's the principle of it and the fact it was my personal ideas and essay plans because now we'll effectively be writing the same things in our exams.