Dude...she is not a dangerous animal, you don't need to "approach her". She is a cute girl, not a lion.
She already knows you are interested as you previously stated to her. Your job, is to not make it weird by putting unnecessary pressure on the situation.
She wants you to keep it light and playful. Be flirty and direct. Make her giggle.
If it was me I would say something like "So, now that you are not with the ball and chain anymore, how about we grab a drink while I hit on you in the most charming of ways"
Have fun. Seduction is charming. It should be kept pressure free (besides for sexual tension), but especially in a work enviornment, you should be keeping it light.
Good luck
