。
She gave away all her clothes to other people.
Literal
She [topic-は] her own clothes [object-を] all people [to-に] gave [completion-てしまった].
みんな functions as a postposed quantifier here ('all of them'), modifying 自分の服. やる is the rough/casual 'to give,' used for things given to subordinates, animals, or in casual contexts where あげる would feel too polite. ~てしまう marks the action as completed and slightly final or regrettable — 'gone and given them all away.' 人に — 'to people' — is a vague generic, suggesting various recipients rather than one specific person.