I agree with you - I think people would assume a Vegas or Phoenix is a boy.So my partner likes Vegas and Phoenix, but to me those sound masculine...plus I think I have come across several Goldens with those names and for some reason I want to find something a bit more creative.
Off your original list, I like Addie the best (because I like the name Addison). But I like Denver and Aspen if you want to link them. (Just consider what shortening Aspen would lead you to if you're calling her...).
You mentioned East coast.. so what about Ocean?