Don't worry, you won't wind up with a bird sitting on your arm.
I have been on this tour twice, once by myself, once with my mom. We are both big animal people, so we loved it. Your sister, if she is considering vet school will be fascinated and it will be a fun thing for her to get to do.
They take the tour groups back into the backstage areas of AK, where all the animals are housed and cared for. You get to see where the elephants live, and where the rhinos live. Both times I went, we got to pet a rhino, although animal interaction is not guaranteed.
They show you the various other living quarters, the food prep areas, the vet facilities at conservation station, and other places associated with caring for the animals. There are places where you can see birds, but we had no bird interaction. then you go to a conference room and a animal caretaker brings in an animal and you get an up close and personal, if you want. On my first trip, it was a baby gator and on my second, it was a little snake. Pretty cool!
After that, the last part is your own group Kilimanjaro safari ride, but with out the Big Red/Little Red story line. They take you through the attraction and point out all the little features you'd never know about unless you'd done the tour.
It really is a great tour, takes about 3 or 4 hours. You'll come out with a whole new appreciation of AK, even if it's not a park you're particularly hot on.
Hope this helps!