Use 'tetchy' to describe someone showing annoyance or discontent. It's stronger than just being irritated. She was quite tetchy after losing her keys again.
Pro Tip 2/3
Short Temper
'Tetchy' implies a temporary state, often indicating a short temper over small issues. Even a little noise makes him tetchy when he's concentrating.
Pro Tip 3/3
Not Offensive
While 'tetchy' suggests irritation, it's not usually considered a rude word to use about someone. My comments were not meant to make you tetchy.