@everyone who mentioned suicide: In all honesty, it would be a good scare for her, but only if later shows that it was something else, like changing a light bulb. Tha would show her the dangerous game she's playing and how could it end.
HOWEVER, she's not the only one at fault. For his perspective, she has already shown that it's just a normal girl with a normal BF that does normal couple things (a.k.a sex), so still pinning for her is just plain stupid. Even if he's in love, letting that love go (or even better, FORCING YOURSELF to let that love go) isn't as painful as what he's going though now (talking from experience). And if he finds another girl, all the better.
...now that I remember, didn't the webcomic had something along those lines...?