wound to the quick

Alainは入院してその後退院しますが、彼がおかしくなったのはドラッグに手を染めたからと両親に疑われます。
As a result, home life had become a little hell. His father wasn't talking to him except in monosyllables, and his allowance was stopped. His mother was doing the "wounded to the quick" act, which mostly involved looking at him with an expression that suggested she had somehow raised him badly, that being the only reason he could have acted this way.
"wounded to the quick" は引用符で囲まれているので一般的な表現ではないのでしょう。まず "quick" に私が知らなかった次の意味があることが分かりました。
・Oxford English Dictinary: (the quick) The soft, tender flesh below the growing part of a fingernail or toenail. cut someone to the quick: Cause someone deep distress by a hurtful remark or action.
・Vocabulary.com: any area of the body that is highly sensitive to pain (as the flesh underneath the skin or a fingernail or toenail)
The noun quick is a whole other story; it's a highly sensitive bit of skin, especially the skin under the fingernails or toe nails. Be careful not to chew your nails down to the quick? especially your toe nails.
となると、 "wounded to the quick" は傷口に塩を塗る様な感じですが、どうでしょう？
上の辞書にもある様に "cut to the quick" と言う慣用句があることも分かりました。
・McGraw-Hill Dictionary of American Idioms and Phrasal Verbs: Fig. to injure someone emotionally. (See also cut something to the bone.) Your heartless comments cut me to the quick. Her remarks cut him to the bone.
"wounded to the quick" は "cut to the quick" の表現を念頭にした著者の表現でしょう。"To add insult to injury" と言う表現を読んだ事がありますが同じような意味でしょう。