You know her name, you work in the same company.
So send her an email. Content is up to you; try something along the lines below.
“Hi, I’m brycerw. I’ve seen you around, never get a chance to chat because we’re in different parts of the office, thought you might like to come for a coffee one lunchtime, I often head over to XXX. Busy today? And yes, I know I’m a cheeky sod for emailing you!”
That gives her a chance to have a think, and either say yes, no, or ‘maybe next week’. If the answer’s a definite no, then your question is answered; anything other than this means either you see her for a coffee and a chat (up to you), or at the very least you’ve established some sort of contact.
If she’s attached, she’ll let you know very soon (or turn you down immediately).