They are strict. They measure at every ride, two times if there's a question before loading.
My son couldn't ride Star Tours b/c at the *second* measuring stick the CM was able to slip a piece of paper above his head, below the measuring thing.
Now, while the CM was busy doing this, a mite of a little girl slipped past wearing heeled shoes...but I'm SURE you don't want to be like that, especially b/c it's for her safety.
And ultimately, the inches are a guide for us, b/c there are plenty of kids who measured the correct height at home, but either were taller or shorter than the measuring sticks when at DLR. The only thing that counts is the measuring stick; each individual one.
So make sure she knows that you will "go see IF you can ride (this time)", each time you are near a ride that's 40". Practice standing big and tall, and don't let that slip at the second measuring stick if she makes it at the first. It's a good idea to NOT carry kids inside the ride, at least in sight of the CMs, because it makes the child obvious to them, and they will generally remeasure, to make sure. And in the excitement of the ride it's easy to forget to stand big and tall, and a child who IS tall enough can shrink by a millimeter, and not get to go when they really should have.
Now with a whole inch? Probably none of that is even going to happen. So prepare her now.
And if you are fortunate enough to get to go more often, I will tell you that the idea of needing to grow for certain rides can get a kidlet to eat so much good food! My son has never much liked beans, even though we're vegetarian and try to not rely on soy protein too heavily. And during our last family trip, when he saw how relatively close to 46" he is, he started happily eating beans to "grow big for Indy". It's been the same way since the Star Tours incident. He eats good for to "grow big for _______" (whatever ride he's yearning to ride). You can get a good amount of good food in 'em, if it'll help their bodies grow!
