You hit the nail on the head when you attributed your fieroucity over this situation to PMS.
You didn't tell your boys about the sleep over, great, they still get to go to laser tag, great. Even if they find out about the sleepover they probably won't feel anything because the kids invited weren't neighbors but classmates. Usually my boys were more logical then emotional about such matters. So things that would bother me didn't ever bother them.
Take a deep breathe. Let them go to the laser tag portion of the festivities and don't take the change of plans personal. It probably wasn't personal at all but possibly logistical or even economical. If you are not used to caring for over six kids at a time then this sleepover could be a disaster for the over committed parents and a few less kids welcomed.
If a sleepover between your kids and hers is what you want, why not host one since in my experience it is easier to add more kids to an already large family than it is to add more to a small one.
Relax and let your kids enjoy the part they can enjoy and know nothing of the change of plans was personal.