As I understand it, the pocket edition doesn't have the nether, multiplayer or java mods. I also ink many crafting recipes are different.
An aside... With no nether, is there no quartz? No daylight sensors? No white palaces?
It's a great intro to the game, but if she wants to have minecraft playdates with friends or learn Java to make mods (modifications to the game) you'll have to upgrade. There's also a part of the fun of the game which is learning/knowing all the recipes to craft things. She'll have to relearn if she switches, but I don't think that's a huge problem.
