All I can go off is your word, but tone means a lot I think. "Nah. I don't like to walk in the city." Sounds final, if someone I liked wanted to go do something I don't, i'd propose an alternative(To be honest, I would probably do something whether it sounds fun or not haha) "Uh, how about x? I hear they y very good z" etc. Personally I'd find that more difficult. How do you go about wording that? I find it helpful just to imagine other people are you in social situations that I've not much experience with(I have a lot of experience not having experience). If you were in the current emotional situation she is(busy?, tired?, happy? etc.) and someone came up to you and said something like "Hey, would you like to go for a walk some time?" what conditions would you need to say yes? How attractive would she need to be? How well would it need to be worded? all the girls I've successfully asked out were already no strangers to me in whatever setting
I have no idea what's at fault here