If I recall Molly, you are a teenager?
At this time in your life - and the lives of your friends - gossip and rumour are absolutely rife, so you need to adopt a nice simple code.
Believe nothing of what you hear about anyone you know, uinless that person has told you him or herself, and you can trust them to be honest.
That way, you will never be caught on the roundabout of rumour and gossip that surrounds you and your peer group.
If you know this girl well enough, and think you need to know - ask her. If not, simply forget about it and move on - it's not worth thinking about too much.