My sister was telling me about one of my niece's friends. Girl is 13 yo. She came over for a sleepover and the girls were all hanging out in the kitchen. They got tickled and laughing about something and Girl peed her pants - not a little leak, but a puddle on the floor. The other girls started screeching and laughing at this turn of events. Girl was laughing about it, too. Niece grabs paper towels and cleaning supplies (they have a leaky dog so she is well training in cleaning up pee) and handed it to the girl (I think the other girls had left the room) and the girl refused to clean it up saying that it was "only a little water."
My niece got my sister and she cleaned it up. Then my sister noticed that the girl hadn't changed her clothes so she asked her if she wanted a plastic bag to put her pants in and discovered that the girl brought no clothes with her to the sleepover - not even a pair of pajamas. So yes, she was sitting on their sofa in pee-soaked pants. My sister gave her some of her clothes to wear overnight and take home the next day. She didn't seem to be embarassed at all and even joked about how this happens to her a lot.
So WWWD? I don't think I'd be inviting this girl over again. I understand having this problem, but 13 is way to old to not be prepared for it, IMO.
I just a friendly gal looking for options.