Agreed.
Paranoia can make anything go sour... sometimes you just need to tell yourself, "She's doing nothing wrong, I need to stop it." Say it quietly to yourself if you must, anything to get the thought there.
It also makes me wonder about your confidence, as well. In almost every case I've seen of this kind of paranoia and worry, it involved the person themselves having low self-confidence. "They'll leave me

" is a terribly depressing, self-degrading thought, when UNFOUNDED. I advise you to consider this, and see if there's a fault somewhere in your vision of yourself.
If she did nothing against -you-, why are you worried? If there's no proof of anything wrong, chances are high that hey, there's nothing wrong.