OP here again, I measured her in Mary Janes because that's what she had on at the time, I believe her sneakers have a little bit of a thicker sole, but she wouldn't change her shoes for me when I asked and we were walking out the door so I didn't push the issue......In no way do I want her to miss the mark and not be able to ride, I just hadn't measured her in a while and was assuming she'd not be tall enough, she was just big enough to ride the 40 inch rides our last trip, I hadn't expected her to grow so much! My oldest is a much slower grower and was just finally tall enough for Space Mountain last year at age 7, big difference between kids!
Nor do I believe we are double dipping or cheating the system, we are using rider swap as it is meant to be used, the same way we have used it for the last 8 years. FP+ or FP-, you were always permitted to use one of your FPs for one parent to ride and get a rider swap pass for the other parent to ride. While DH is riding with his FP, the kids and I ride something else with the other 3 FPs and then DD1 and I use the rider swap pass to ride the height restricted ride. No cheating, just the system Disney has developed. If DH, DD1 and myself all got FP+s for the height restricted rides (like Space Mountain) there would be no need for us to get a rider swap pass at all and poor DD2 would be feeling really left out with no way to use her FP+ and waiting around for an hour for the rest of us to finish riding the height restricted ride.
I guess for now we will keep our FPs as is since she is too short as of right now and get a measurement on her again in her sneakers right before we go and change our FPs if necessary.