Silent Witch: Chinmoku no Majo no Kakushigoto

Monica Everett is the Silent Witch, the only mage in the world who has mastered the art of unchanted mage craft. But Monica hides a secret: The reason she learned to use magic without speaking is merely because of her extreme shyness. Until now, she's been content living a peaceful life hidden away in the mountains, but an unexpected visit from a colleague brings her a task more daunting than any other. Now, it's up to the world's shiest mage to infiltrate an academy and protect the second prince from danger...without letting her fears get to her!

(Source: Yen Press)