Right guys, I want advice on how to number close a co-worker. Apologies in advance for the convoluted nature of the scenario (Skip to last paragraph of you want!) but here's the situation:

I work in a call centre and have recently gone back to my old department because I hated the one I was working in. But in the last week of working there I was asked by my manager if a HB8 could sit with me for an hour for an overview of the job as she was considering applying. Turns out she works on the department I was going back to.

I was flirty, friendly and confident. She was interested and by the end of the overview she was even talking about seeing back in my old department. (So charming she decided not to even apply )

So I start back at my old job late last week and even though this girl is within eye contact, layout and logistics prevent "natural" interaction. But I decided to act fairly quickly and Friday last week I just walked over and started conversation like we'd left off last time; "Hey, how's it going, good to see you... etc."
It went well, she was really intersted and leaning forward as I spoke, laughing, lots of eye contact. After a little bit I said i should probably get back to work and left. Now I just need to know how to number close her. It's obvious I'm going out of my way a bit to go to her desk but is that o.k? Also asking when other people are around, does that matter or am i being a pussy? Once I've got the number it's all good, i'm good with phone game, just need help making this step!!

ANY HELP OR ADVICE IS GREATLY APPRECIATED