She started school a few weeks ago and now she loves this boy so much. Every day she asks me when he can come to her house to play - and I have mentioned it to his mother, who seemed not that keen (early days I suppose). Today was dd's b'day party, and she said afterwards it was good, apart from when this boy didn't play with her. Every present she opened she said "is this from x?" - when she got to his present she was disappointed with it though. Then we looked at the photos and she kept saying "where's x, where's x"
Best thing you can do is not make a fuss about it.
They are fickle creatures at this age - chances are it won't last long. If she's anything like dd was in Reception (and every other girl in her class) it'll be another boy next week. Then it'll probably be a girl, then another boy - or maybe even one of each!