why do some girls let their happiness depend on guys?!

This is my friend, she's been in a so- called relationship for over a year, but always comes crying to me when he doesn't want to see her anymore. We've been friends over 13 years but omg this is annoying to have her go against my advise of dumping him. Why won't she listen, does she secretly enjoy the drama she creates and thrive off the attention? I'm trying to be sympathetic but I hate this guy and how he treats her but she constantly goes back to him even tho she's agreed to me before it will never end good. 
What can I do that she'll listen to?