At least from what I've seen so far, there has not been any other character like her in the game. That leads me to believe she's either from a different world like Aether & Lumine, or she's a part of a pixie type race we haven't seen yet.

Either way, her lack of memory is very fishy.

What if she's actually a herald of the Unknown god who was tasked with keeping an eye on you to make sure you don't jack up Teyvat. I could totally see her doing a 180 and unleashing some super power she's been hiding from the beginning.

Also, is it ever Explained what happened to the original world of the travelers and why they were traveling in the first place?