I was with a guy, a friend of mine, and we were cruising in my car. A girl(HB10) that I only saw for a few times(not dates, just small talk), stopped me for a cigarette, i don't smoke in my car. So we got out of the car. She tried to start a conversation, asking me about a bunch of stuff, then asked me about the car(we have the same brand)...she even got in to take a closer look but i didn't do anything to continue the conversation, i just answered and nothing more and then, after about 10 min or so, she left.

The situation seemed a bit creepy, cause my friend just stood there, near the car, watching the two of us talk so I felt like I couldn't do more because he was around.
I really wanted to continue the conversation and build some rapport.

Any ideas on how should i continue in a situation like this?