Portland lesbian here. A few of months ago I started hooking up with a friend of mine (she initiated). She had a long distance boyfriend and I knew that but after the first time she told me that the two of them were taking a break. I took this to mean that she was free to see other people and kept hooking up with her. A month later she clarified that wasn't the case but I still kept hooking up with her. Since then she ended it with me to make it work with the boyfriend and then subsequently ended it with the boyfriend. Now she and I are back in old habits and I'm trying to decide where I want to go from here.

The sex is amazing but not only that we have had some really good times together. Good talks, lots of texting, an actual long walk on the beach. I'd like to keep dating her and see where this goes but I'm worried that her cheating on her boyfriend means she'll ultimately cheat on me too. And our communication could obviously be improved. She says she's never cheated before. Is once a cheater, always a cheater really a thing? Or is there some kind of one-time exception for cheating at the end of a relationship that really wasn't working anyway?

Helpful Outside Persuasion Is Needed Greatly

"Once a cheater, always a cheater" does seem to be a thing—although it may be more accurate to say "once a cheater, somewhat likelier to cheat than someone who was never a cheater." HuffPo:

University of Denver psychology graduate student Kayla Knopp studied 484 unmarried adults aged 18 to 35 to find out if people who stray in one relationship are more likely to do so in the next. Her findings were presented at the annual American Psychological Association convention in Washington D.C. Knopp and her fellow researchers asked participants questions such as, "Have you had sexual relations with someone other than your partner since you began seriously dating?" and "Has your partner had sexual relations with someone other than you since you seriously began dating?" Those who admitted to having sexual relations outside their relationship were three and a half times more likely to do so in their next relationship as well, Knopp explained to The Huffington Post in an email.

The study didn't include same-sex couples, HuffPo notes, so your odds may be the same, higher, or lower. But "likelier to cheat again" by whatever multiple does not mean "destined to cheat again."

The likelihood of a cheater cheating again, in my opinion, depends on the reason(s) for the cheater cheating in the first place. Someone who cheats because she's easily bored, aroused by risk-taking, or to punish her partner seems a highly likely candidate for future cheating, HOPING. So you'll have to contemplate why she did it, HOPING, not just that she did it.

And, yes, your potential new girlfriend may deserve a pass since she was cheating "at the end of a relationship that really wasn't working anyway." But if cheating is how she breaks up with people—if that's how she gets out of relationships that aren't working—that's not a good sign.

So ask yourself: Being cheated is a violation that you can only aid and abet, it seems, but is it one you can forgive and forget?