It's like... an honorific. You add them onto the end of people's names to be more formal and stuff. It changes for each situation, but you can save chan for younger kids, pets, girlfriends, siblings, even boyfriends.

That's why I call you Lizzie-chan, because it's more polite I guess. It's just what I'm used to, I suppose.

[She makes a mental note about the durable dress thing, no sweat.]

I wish I wasn't low on clothes; I only have two outfits with me.

[She slumps her shoulders ever so slightly. Life is tough when all you have is a tracksuit and a school uniform.]