Not sure if it's right but it sounds good.
Intro:
E-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-|
B-2-2-2-2-2-2-2-2-2-0-0-0-0-0-0-0-|
G-2-2-2-2-2-2-2-2-2-2-2-2-2-2-2-2-|
D---------------------------------|
A---------------------------------|
E---------------------------------|
Verse:
[ Tab from: http://www.guitaretab.com/k/katy-perry/257444.html ]
You think i'm pretty...
E-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-|
B-2-2-2-2-2-2-2-2-2-0-0-0-0-0-0-0-|
G-2-2-2-2-2-2-2-2-2-2-2-2-2-2-2-2-|
D---------------------------------|
A---------------------------------|
E---------------------------------|
Before I met you...
E-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-0-|
B-2-2-2-2-2-2-2-2-2-0-0-0-0-0-0-0-|
G-2-2-2-2-2-2-2-2-2-2-2-2-2-2-2-2-|
D-0-------------4---2-------------|
A---------------------------------|
E---------------------------------|
Chorus: Same as in the verse or chords:
D, F#m, E
It's not accurate but I think it's close enough and easy to play. Play it a few times
you'll get the hand of it.