center of conversation

After eating a quick meal in the car while running errands, the girls had finished their drinks and were munching ice. My mom overheard the following conversation:

M1: M-you spit on me!

M2: {straight faced} No I didnt. It just pooped out of my mouth.

M&M: Granny, why are you laughing? Whats so funny? What?????

Granny: {No answer because she is still laughing}