S.,
Our now 13 y.o. son had cranial radiation (radiation to the head) when he was 6 y.o. as part of his treatment for leukemia. We recently had to take him to Scottish Rite for GH deficiency testing because he is very short. (He passed all the tests so he doesn't need the growth hormones.)
The testing takes at least 6 hours (but you'll be there all day), and consists of your daughter being hooked up to an IV while they give her medications to stimulate the pituitary gland to make the growth hormones. Other than the IV insertion it is painless and she will actually sleep - very deeply - for part/most of the test.
In order for her to receive the GHs, she will need to "flunk" the tests. "Flunking" means her body isn't producing enough hormones - the endocrinologist can explain at what levels she "flunks". (For our son, it was levels of less than 10 - that number might be different for younger children.) If she "passes" the tests then GHs aren't an option (as was our son's case).
The growth hormone therapy consists of getting a shot every day for X number of days (X being determined by the endrocrinologist), but is usually a year or two - again, you'll have to talk to the doctor as it might be different from a teen's. The shot itself is easy and not that painful I believe. It's a little box that you press against their abdomen and press a button. Pop and it's done.
If you decide to have the testing, which I highly recommend if your doctors are recommending it, take at least one set of extra clothes and see if you can find a swim diaper or Pull-ups your daughter's size. The meds knock them out cold and they run a lot of fluids through them - they tend to have accidents while they're "sleeping."
She also won't be able to eat that morning and only able to drink water. I would make sure she drinks water for breakfast, etc. b/c you want her veins hydrated and easy to find. But for yourselves, take snacks, a lunch, etc. Once she's asleep you can get something to eat, etc. Also, it takes a while to get back to the infusion rooms (at either Egleston or Scottish Rite) so you'll want to take some things for her to do while you're waiting.
If your daughter does "flunk" the tests (usually takes 1.5-2 weeks to get results), I would recommend you do the GHs - especially since she's a girl and does more growing at a younger age than boys who tend to shoot up in their teen or later years.
Feel free to write me if you have any questions. We were just at Scottish Rite a week or two ago for this test AND know Egelston pretty well so if you have any specific questions about either campus I should be able to answer them. I hope everything works out and good luck!
D.