這句英文是什麼意思？

‘I’ve let her look at my football cards, haven’t I? I said she could watch my football practice didn’t I? and today I’m taking her to the biggest and best stamp exhibition ever – with a chance to see the world cup! You’d think she’d be over the moon wouldn’t you? But what did she say?

當中「You’d think she’d be over the moon wouldn’t you?」是什麼意思？