Rodney

Once a cheater, always a cheater? No. But this isn't just once. There's a pattern here.

I don't think she's ready for a real relationship; she's not ready to make the hard investment (tell the truth when there's a relationship problem) or take responsibility for actions. Rather than say "we're breaking up" or "I cheated with somebody" to her current beau, she's basically said whatever's necessary to 1) keep things calm and avoid conflict while 2) continuing to do what she wants.

Based on her history, the real issue is whether she's ever going to be completely straight with you when it's time for a hard relationship decision. I suspect not. And that lack is actually more fundamental than actual cheating -- and can lead to cheating. And in her case, has.

I don't know if you'll be able to trust her. She may not be a bad person, but sounds like she'll always tell you what you want to hear instead of talking it out. (She's only 19, probably still thinking like a teenager.) So you'll go around thinking reality with her is "A" while in reality it's "B".

And then, who knows? Down the line you get one of those "I just stopped loving you, I don't know why, it's not anybody's fault" lines. And later you find out she's been seeing somebody else....