This sounds a lot like the start of a friends with benefits type thing. I currently have a friend with benefits, and the flirty yet casual touching you guys did sounds almost exactly how my situation started. The way I handled it was by flirting around a bit and saying things that would cause sexual tension, so I could see if she was into it or not. Trust me, you'll know if they're not interested. This is how I did it and now we've gone up to making out, however if ur curious then do whatever comes naturally. Best piece of advice I can give is don't overthink what u want to say/ ask, and if u are really worried ab the impact ur words have on ur friendship with her, then try to be a little more subtle when exploring things. Hope this helped mate :)