Swear to God, this sounds exactly like someone I know (related to). Late to EVERYTHING, never brings a thing and stays to eat, then leaves.
Used to bother me too. But, now I don't invite her. Not even to family functions (she's a close family member too) and don't care if she shows up late to the events she is invited to (that I am not in charge of) because I already know the deal---its all about her, all the time. Everyone else knows too, they are just being polite.
And this particular family member COULD afford to bring stuff (single, no kids, alleged good job), but still never did. Never made an effort and was never called out on it. So, whatever. But I'll tell you whats interesting and a bit sad: this same family member now CANNOT afford ANYTHING...long story but HER OWN FAULT. And still, no one cares. She made her bed....just saying.
IGNORE HER PrettyGirl. Karma....its a bitch.