Don't people understand that being "not mean" or outright "rejecting" someone leads to more despair eventually?

If that girl said she didn't like you (I am uming she did since you said you moved on) then she probably likes you more now because you moved on! Playing hard to get in a way. Also, people don't like to let anyone down because to be honest we crave the attention even if the feelings aren't reciprocated. Anyways, I think you should always be honest about your feelings, although sometimes it's hard. And if you don't like someone you should be diplomatic in the way you let them down.