Maybe I have a comprehension problem, but I don't see any of the girls or even the guys condoning this boy/man's behaviour. What everyone here has been saying is that it's a bit stupid of her to let him use her, when she knows that that is his only purpose. She doesn't come across as very smart to me. As I don't see the guy losing out on anything. And frankly I don't think he would care much if in the end she goes and marries someone else, because he's not concerned about owning her emotionally, he just wants to have easy sex and is getting it. So how is his ego going to get crushed?
My thoughts, exactly.
The girl is just wasting her time... if she knows there is no future, why not get up, dust off, and move on. She has already wasted so much time on someone who has no intentions of marrying her, she needs to break loose of the "relationship" (or the very little that remains of it) and find someone who is willing to make a long-term commitment to her.
There is absolutely no need for her to linger around in an attempt to give the guy a "taste of his own medicine", when it's clear to her (and all of us here) that he has already moved on (emotionally, mentally) - it is time for her to do herself a favor and put an end to it all. She deserves better.