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