No matter where, when, or what, Anna is a constant presence in the worlds of Fire Emblem - the same name, the same face, the same personality. The same game. She's here to make coin, and perhaps do a little bit of the right thing on the side, if it helps her friends. Many mysteries surround this omnipresent merchant... too many to name, too many to explore, too pricy to be bought.
No amount of coin will make her give up her secrets.
Secret Seller Anna is a rightful god. I'm running with that. The dragons - nigh divine entities - were being driven mad by the force of their own powers. Forced to re-create themselves into humanoid forms to save their own sanity, they shunt the brunt of their power out of their own bodies. This is what has happened to all Manakete, in the end. Though, not all dragonsl wished to take that form... and it's safe to say, that other methods were attempted as well, before the tried and true one was successfully discovered.
This Anna - all Annas - are shards of one of these early dragons, an entity of commerce and civilization, whose crafty attempt to try and preserve their identity went a bit awry - scattering their soul across space and time, across multiple timelines and universes. The various shards, their other selves, 'sisters', each and every one. They aren't upset about their situation, though. More territory, more coin. What people don't know won't hurt them.