This exact exchange just occurred between me and Edie at the breakfast table:
Edie has a giant sneeze. Then she looks at me in an accusing way and says: "BESSYOU!?" (as if to say, Why didn't you say bless you Mom? SO rude.)
Me: Oh I'm sorry, I forgot to say "bless you!". Bless you Edie.
Edie slowly shakes her head at me in silent disapproval and then adds: Sheesh