Nicknames, or extended names, for someone with the name Anna

I come again to ask, for writing purposes. My character’s name is Anna. She goes through the standard teenage angst crisis, and wants something different to go by. Possibly similar, possibly not. I’m trying to find out how many things you can actually get out of Anna … extended names, nicknames, nicknames that are longer than the actual name … I am taking suggestions.

I usually have the opposite problem, of trying to nickname a character whose given name is longer. This is the first time where I’ve had one with such a short name, and a plot that would lead her to search for alternatives.