While a party for her is being thrown downstairs: "Maybe if I stay up here long enough they'll decide to just leave me alone."
Yuri, aka "Iron Violet The Shy Titan" is a very shy and insecure girl. Abusive Parents is implied to be the cause of this plus past bullying. Due to the kindness of her best friend, and her adventures as a superhero, she's slowly attempting to overcome this. She's taken on a robot girl with super-speed and a fire-throwing supervillain, yet she still blushes at the thought of wearing a miniskirt.
Neeka from Late Blooming is impossibly shy, to the point of hardly ever talking to anyone and putting all effort into avoiding contact with people.
Mina in Alien Hand Syndrome isn't completely withdrawn, but she's certainly awkward and uncomfortable in social situations. Her friend Erin alternates between making fun of her shyness and trying to cure it.