I'm thinking of missing my sisters wedding because my fiance had a panic attack
Was the panic attack so serious that you feel that he won't be able to go?
It really was. It happens when he's around a lot of people and he can't breathe.
That is unfortunate that this happened. It is important to be there for your fiance, so I understand not leaving him.
I feel really bad about it.
It is out of your control. You can make it up to her somehow, but the health of your fiance is more important.