Who is that?

I'm not who I was
I haven't seen me in a while
There's a pretty girl in that mirror
I can't remember when I stopped being her
Or maybe she, me
She's trapped in a rectangle
With bad lighting no less
I see her window shopping
Or watching the trees rush by
Quiet, observing
Raised eye brows and squinting eyes
A ripple in the water and she's gone
Day by day I didn't notice the change
But suddenly it stops feeling normal
Suddenly I'm just not me
And she's just as confused
Our synchronized dance in time
I kind of want to smack that smirk off her face