The Anime Lad
Monica Everett is celebrated as the only witch capable of casting magic without speaking. This extraordinary technique exists because she finds conversation unbearable. The Seven Sages assign her to secretly protect the second prince at school, where anonymous competence is less useful than introducing herself and maintaining a cover.
Super Eyepatch Fox
Monica mastered voiceless magic to avoid speaking, becoming famous for a talent born from severe shyness. Then she receives a covert assignment at a school attended by the second prince. She must protect him while staying anonymous, which requires classmates, conversation, and a credible school life.
Gigguku
Monica is powerful enough to cast without an incantation because she was THAT determined not to speak in public. Then the story sends her into a school on a secret protection mission, where ordinary conversation may be harder than magic. Her ability is thrilling, but the premise gives every small social step equal weight.