woowoo,
I can't give you any guarentee about your girl friend's safety. Nobody can unfortunately. It is just that OCD causes irrational worries that most likely will never come true. I Know this is probably not very comforting but there is a need for truth also.

I would also recommend what the others have, that you get some advice and help from a professional. Perhaps you could talk to your girl friend about these thoughts. This may help to ease your distress.

Take care and keep posting if it helps.