But I got the number of a girl that I work with. I know the policy is generally not to shut where you eat but she's been giving me IOIs for some time now. My question is how to proceed.

I tried to set up a date for this week but she's busy on the nights she and I are both free. In the meantime I'd like to build some rapport out of work. She's young so I'm guessing text game would be appropriate? Thoughts?