You shouldn't leave events early without notifying people.
Jill is at a social event with friends and something urgent has just come up.
Jill wants to leave in a hurry.
Jill texts her friends about the situation before she leaves giving them a heads up.
Jill leaves without bother saying anything to her friends that are there.
Jill's friends understand and are glad she was able to be there for a bit.
Jill's friends thinks they have been ghosted and are taken aback.