To show desperation I gave her unstable posture, whichever way her hips go, her chest goes the other way to counter balance her fidgeting. She is squeezing her inner leg muscles and bounding from one leg to the other. The hips and chest make strong motion gesture, and this is where i put the shake lines.
Sometimes I think drawing the bladder is a little too wierd, but its the easiest visual indicator to what is going on. I think because its round and pink its cute, and i feel empathetic for it stretching. Its sometimes more cute to use other symbols.
After she makes sure nobody is looking, she will let go, relax, and go inside to get cleaned up. It is a pretty appropriate place all things considered.
I love the details you described