She arrived late to her friend's party.
Did she give a reason for showing up late?
No she didn't say anything about it.
If you tell someone that you're going to arrive on time for a get-together, then you're supposed to show up on time. If she keeps doing this then people might stop inviting her to things.
Who cares? I just want to be able to hang out with my friends whenever I feel like it! If I get to go late because I feel tired, why shouldn't she?
I get what you are saying. Just I think it might be good to let other know if you will be late so they don't have to wait around.