Cuteness overload! Both girls are adorable, cute, sweet, lovable. They both share a competition with Vanellope and Agnes over the cutest characters ever. I've seen girls who look like Boo and Bonnie before, and I hope to have a daughter (or son) like one or both of them
No, she's really just a young girl who has an important role in Toy Story 3. You obviously haven't seen it yet, so I'm not going to tell you anything else. If you really want to know, I suggest you go find yourself a DVD copy of the movie, and then go watch it.