Why does my girlfriend only act mushy gushy in public ?

She calls me by my full name in private. She Doesnt use any cutesy, endearing names in private. But when we're in public like on facebook she writes on my wall stuff like " bottoms up buttercup". Love you my adorable my little snookums. ". " hot stuff". " babe". " loverboy". " sleeping beauty". And think she might do to that to annoy my ex girlfriend who's my friend on fb but I'm not entirely sure.