I love how sensitive she is - everyone on the team is, in fact, but since they have to deal with such horrible things so often, they need to get a tougher skin. But Garcia, it's like she refuses to lose her "innocence" even though she must deal with those things too.
I think Hotchner was right on when he said she had so many colours and happy images in her office to remind her to smile/think positive even though there's so much evil in the world.