。
She inherited her temperament from her grandfather.
Literal
She [topic-は] that temperament [object-を] grandfather [from-から] is-inheriting.
気性 ('temperament, disposition') describes someone's innate character — quick-tempered, even-keeled, stubborn — distinct from the more general 性格 (overall personality). 受け継ぐ pairs 受ける ('receive') with 継ぐ ('succeed, take over'), giving 'receive and continue' — the verb for inheriting traits, traditions, family businesses, even bloodlines. The ~ている here marks an enduring resulting state: she has inherited it and continues to embody it. から marks the source of inheritance, while を marks what's being inherited.