Considering transition when you've got a Very female alter should sound like a no-brainer.
As it is, it's almost Superfluous. if Keri's out, Passing isn't a Question. She goes right to the part of other people's brains that remember Mom, and dances on top of it.
Also, there's Voice Training, and then there's what She does. Like to the point she's coaching some of our trans friends on Passing with Voice alone.