Before anyone jumps on you for trying to "help" (and they will) I'll sympathize. I have a 7 year old who ranges in height from the 3rd to the the less than 1 %ile for height. To make it worse, she's a twin, very skinny, and her sister is average, meaning she towers over her, everyone assumes they are big/little sister, DD gets called out for stuff like going off the diving board at the pool, unthinking camp counselors move her to the preschool group without even asking her how old she is. . .
Disney CMs are strict. You will not get into a ride by "almost" making it once they measure you. When DD was trying to make the 40 inch mark a couple of years ago, it was tough. We were measured at every ride and in the mornings she made it a couple of times, but if she didn't, then none of us rode. At Hollywood Studios, she couldn't ride Star Tours and my husband really wanted to go, so he took her sister on and I bought her a Yoda "judge me by my size do you" pin and an ice cream. There were a few tears then. Our last day she was dressed as Ariel and had on her Ariel shoes while we went to Big Thunder Mountain. She didn't even get questioned--completely unintentional on our part. I wondered if we should have just put her in heels the whole time, but then I knew that would have hurt her feet and also been sending her the wrong message.
I think that at 43 3/4, regular supportive play shoes will probably give her the extra quarter inch, won't they? I'd go on the height restricted rides first thing in the morning when I hear you're taller, and practice standing straight and proud to extend to her full height. If she feels embarrassed, she might slump.
We're going to have the same issue for our December trip. We'll stick with the family rule that either we all ride, or none of us do. I wouldn't do that with different age kids.