Am I being paranoid and what should I do?

If she is or isn't doing this there I nothing you can do to sort ou the situation. What you can do is forgive and forget. It might feel annoying and frustrating! But think about what it is doing to you, it's causing you hurt and anger thinking about it. The best thing to do is try and be her friend since she's family. Everyone has a crazy/annoying person they have to deal with in ther family. The best thing you can so is not let it get to you.