Actually, she might not know that alternatives to monogamy exist. The LW should check out "The Ethical Slut" by Dossie Easton and Janet Hardy.

Another reason she may be dating the monogamously inclined instead of like-minded partners is that she gets a thrill out of deceiving them. Also shrink-worthy.

It's totally reasonable that a poly woman could live to 22 without actively seeking out (or passively finding) poly partners - not because she enjoys hurting her monogamous partners, but because there just aren't that many poly people. And even when there are, it's hard to find or create a community in most cities. Living in Seattle and being the target of thousands of letters from poly cuckolding swingers has skewed your perception of how easy it is to find yourself a poly person, Dan. Even avowed polyamorists often take until their 40s or 50s to find polyamory and happiness.

No advice on keeping the specific guy whose goodness prompted the letter, though.

Not having "any guilt" is definitely a key point. Knowing you're hurting someone and breaking your promises should provoke feelings of guilt, regardless of whether you're poly or not. Whatever she feels, exploring what she wants and needs with a therapist will be a great help. Keep looking until you find one that clicks - the wrong therapist won't help at all.

If she wants to be non-monogamous, she should read all she can about it. If there aren't many poly people around because she's not near a major city, she should move, just like gay and lesbian men and women tend to move to the city. SF has multiple poly scenes, for one.

If she doesn't want to be poly, and just wants to cheat but not have her partner be with anyone else, then she's just your average skank. Harm reduction: use condoms every time, get regular (every 3 months) testing, and ask specifically for each test, since they tend only to test for 3 things if you're a young female.

Sounds like a fucking basket case. I wonder what ever happened to this person. Probably nothing healthy.