Paul,
What a wonderful brother you must be. I have two just like you.

I'm so impressed that she is going to her sons concert and also understand...........we mothers will do just about anything to witness our kids triumphs. I think she is smart to find a way to cover her surgical site for this event, I know I would do the same if it were an event of my childs. Our kids might tell us they don't care, but trust me, THEY DO when it comes to their functions. I have a feeling that your sister is trying to hide far more then some stitches and swelling. When I had surgery on my mouth a year ago, it was a MESS for about 2 months afterwards, very swollen, discolored, just unnatural looking. I was coaching at the time and I kept the area bandaged when I went out. There is some wonderful stuff that is skin colored and it stays put. Have her fill the cavity with some gauze. If the cavity has any drainage in it, make sure she wets the gauze with saline or something so it won't stick.
I'm so happy she gets to go, sounds like she's had one rough road.
Take care,
Minnie