Lactose Intolerance?

He sits at the table, celebrating his friend's birthday.  They eat cookies and pile on the ice cream, syrup and whipped cream. Their laughter fills the room as they devour the sugar overload in front of them.  She brings out the milk, offering each boy a glass.  Each one gratefully accepts, inhaling a refreshing sip, until she reaches the last boy.

"I don't want any; milk doesn't agree with me."

"Then tonight's going to be a great night," she laughs to herself, as she returns the milk to the fridge.