Throwaway for obvious reasons.

My friends and I have been planning a group get together today for the past week and a bit, we've had a date and time preplanned for people to show up etc.

The day of, one of our small group (we're a group of seven, we only see each other once a week if we're lucky) says that she can't make it because of another thing she has to go to that's she's known the date for for weeks, just not the time that she found out last night would overlap with our preplanned get together.

I think that if she knew she'd potentially be busy on the day, she should have said something so we could have pushed the time back a bit without messing around with other people's schedules. Instead, she tells us five hours before people are supposed to be meeting up.

AITA?