I'm currently talking to a girl I used to work with:

We always had a flirty relationship and we'd text a few times a week after work but we worked in a corporate setting so it was discrete and our interactions were somewhat "work appropriate." One time we were at lunch with our coworkers (who we're friends with) and the two of us pretended to be a married because they had some anniversary discount; months later it is still a running joke that we are a married couple.

We kissed a few times recently after work (soberly) but it was only after I got her to meet me somewhere for some innocent reason and the times I was more straight forward by basically saying: "come over/lets hang out" she'd come up with some lame reason that she couldn't (maybe she requires a lot of plausible deniability).

When we text its basically just flirty banter with both of us being sarcastic smartasses but I think its starting to get old and now that I just stopped working there for a new job I don't want the flame to go out.

How do I transition the texts/interactions to something of more substance and comfort?.... Something where we at least acknowledge that we kinda like each other and then hang out socially to see where it goes

Logistical Issues:
1) I live with one of my former coworkers who is known for his lack of discretion (none of our coworker friends know anything is going on between us and I'm guessing she'd like to keep it that way)
2) She lives kinda far away but if she were coming to my place from work its a short drive


Any advice is appreciated!!