nice or kind
Hello again! In terms of "gentil" meaning kind or nice, as I have been living in France for 20 years, I can explain it this way. Out of context, it's hard to know, but if the invitation was to visit the man in his country and stay at his place (a kindness), then kind is the right choice. However, if the invitation was to go to the cinema or have a meal or a drink, then the woman was giving the man a "brush off" ("un jour peut-être" is a way of avoiding future invitations) and the word "nice" would be the appropriate iterpretation. I am a woman, and we have a hundred nice ways of saying no, so about this I am sure.