They way they respond when you're going thru hard times. Not just possessing sympathy and empathy, but do they help sooth you and see you thru it? Do they listen and try to get a real good picture of what you're going thru? Do they try to help solve the issue? Or does she tell you it aint' that bad, or you should move on, so she can talk to you about work and shopping for hours?
Problem is, you can date a person for months and everybody is great and you not see this come. Someone is sick close to you and they act like it's nothing and can't put their pity grievances with you on hold.