Did she want to start a conversation?

Ok so I went to the gym as usual today and my house is an apartment which is one of the apartments in two blocks of apartments. so I thought as usual the gym would be empty as it is everyday but today there was this girl. I just can't figure out her age,must be around 19-22. I don't even think that's right,I'm so bad with guessing ages. So she's doing her warm-up and stretches, and I just go and start my workout. Through out the whole of my workout time not a word from both of us. But suddenly when it was time for her to leave she says excuse me. But I was on my exercise so I couldn't reply so she waits for a few seconds and then leaves. I had just 2 more reps so I did them and got out the door just to ask her what. She says "do you mind if i kept those lights on or should i have turned them off because i see you still working out". I just say"Its ok" and I return back to my workout. Now I feel so stupid not talking because when I thought of it later,the only reason I could think of why she asked this is because she wanted to start a conversation. Because It really didn't matter whether the lights on the other side were on or off because I had finished my set and then spoken to her.BTW I'm 19. So you guys think I should have said something like"it really doesn't matter now because I just finished my set ....so......and so on ".