Interesting concept, but I ran into an issue where the girl wouldn't get angry when the coffee got cold, I think the girl should get progressively easier to anger as the coffee gets colder and automatically flip out when it reaches room temperature.
It also seems to me that the game kind of encourages the player to just add little splashes of milk, foregoing sugar entirely. Perhaps it would be more interesting if the game somehow pushed the player to risk being more liberal with the milk or even dropping a sugar lump every now and then.