Fiancée shows up to Christmas breakfast 2 hours late, gets angry at fiancé for allowing people to eat before she arrived: 'It's unfair to punish everyone for one person's poor time management.'

Imagine going hungry for two hours because someone's girlfriend was late to Christmas?

How you manage lateness has a lot to do with what kind of family you grew up in. Your family either tolerated lateness or they didn't. For example, let's say your family wanted to see a movie at 2:30 and invited Aunt Beth to come along. If Aunt Beth hadn't shown up by 2:30 or even 2:50 and wasn't responding to phone calls or texts, what would your family do? Would they go into the theater and text her to meet y'all in the seats, or would they miss the original screening, buying tickets for the 4:15 show after she finally showed up at 3:30? The latter family tolerates lateness; the former does not. 

If you grew up in a family that would wait around for people with poor time management skills, you probably have no tolerance for late people in your adult life. In fact, there's a good chance you show up chronically early to events just because you hate waiting around for other people so much. If that's you, I don't blame you at all. People schedule events at certain times for a reason. If we're supposed to be having dinner at 8, you're going to show up hungry enough for dinner at 8. If your dinner guests don't show up until 9:30, you're going to be crabby and starving by the time you actually eat, and the meal will no longer be a pleasant experience.