work girl whose seems picky

so, i work in department A and this girl works in department B. She is new and we just made some eye contact for 2 weeks straight, then 2 weeks later, I ran into her at the photocopier and made some small talk.. nothing too fancy.

yesterday, she was in my office with another colleague and we stared, then i decided to make fun of her, and told told everyone to text her more often because she's lonely and need company off work hours.

I added her on facebook last night and whatever, i bumped into her at this metal door and he crashed into each other, and I was ike great! you ruined my day and she's like "sorry" and kinda kept walking towards her office.

I get a text from her 1 hour later, "great running into you, NOT really! "

we continue talking and led to talking about jobs and other stuff and she seems to be impressed with me and takes every chance to make fun of me, I don't know how to escalate this, simply because it feels she's doing more flirting ad I think I'm being boring.... I don't work in the same floor as her, so i don't see her everyday nor do I want to.. just to make our sightings more special. How can I make this girl crazy and approach this to standards of a true PUA??!