A member of your crew meets a girl, dates the girl and fall in loves with the girl. From this moment on, he no longer hangs out with you or your crew and spends all his waking hours with the girl.
Chris: Where's Andy these days? I haven't seen him in ages!
Welly: He's round at Lou's, again. That's the third day this week and it's only Wednesday!
Chris: Fucking girlfriend sellout.