i was in the exact same situation a few weeks ago, but i´m very new to the game so my advice may be crap. you´ve been warned.
we had mutual friends, so i got this girls msn, instead of facebook. and i think that i came off as a bit weird/needy/desperate.
we had some attraction going, and you seem to have as well. so it might work out.
(i´m meeting this girl tomorrow)
but, i think i would´ve handled it a bit different if i could do it again.
just be patient and play it cool, and wait until you two meet out at a club/whatever again instead, and game from there.
get her number instead of adding her on facebook, if you don´t close.