Here is a relevant story for you. When I was with my Girlfriend, she met a lad in college. I knew they was friends and I didn't care as he was nothing more than a friend at the time. However, I got to know he fancied her from the messages he sent her and eventually we split up over various other different things and they became an item.
We used to text still and once he phoned me and told me to leave his Girl alone, as she was with him now and they were very happy. Not 2 days before that conversation she was sat in my car telling me how much he annoyed her, and how we should get back together. Over various reasons we never, and they stuck together. Now and then he'd phone me because he'd either seen us together or I'd phoned her while he was there and again he would reassure me how they was in love, and how I was jealous and needed to accept that they are happy. The next night I slept with her in down the local promenade.
They never lasted much longer, and I knew all along the poor bastard was being used, and used badly. Once we was even shopping together when he phoned to ask her had she seen me, and was I still harrasing her. How much of a mug was he? When I asked her why she was with him then? She said it was something to do.
All I am saying is, make sure this doesn't happen to you as this lad was sure he had found the real thing, when all along she was just another slag. Her feelings for her current partner won't just go away over night, so it's not as though it's like a fresh start as it won't be. I'm not saying she isn't the one as she could be, but be careful. Don't go in blind and listen to your friends. A good friend will be looking in from the outside, and tell you what you need to hear. Not some sugar coated load of shit to make you feel happy. I wish you all the best.
Benni.