I have a female rogue that has lost her memory. She's 18, and woke up in an alley two years previously with no recollection of her prior life.
I'm looking for ideas to explain how she lost her memory...
Her name is Maia, she's a huge flirt, but has a genuine heart.

She has a twin. They were both kidnapped and she sustained a head injury in a plot to free both herself and her twin. Her twin got away at her urging, and her kidnapper left her believing she was dead.

Maybe talk with you GM. Your memory loss could potentially work in with campaign plot well, and that's often really cool when it's done well

There isn't really a campaign... I just role play with a friend. We each have multiple characters and take turns being the gm

You could skirt past it and have your character move on likely I did with my Rogue named Orka Dimondback, a Kobold who doesn't remember the first 7 years of his life.

That's what I've done so far.

I actually know a pair of twins IRL and one of their names is Maia. Freaky.

@222daisy May I suggest it turns out the twin is evil or, even better, the character is evil and was rescued by the good twin?