。
She's deeply concerned about the result.
Literal
She [topic-は] that result [object-を] greatly is-minding.
気にする — literally 'mind one's spirit' — is the everyday Japanese expression for 'worry / care / take seriously'. The ~ている here gives it a current-state reading: not 'is in the act of worrying' once, but 'is in a worried state about it'. 大変 ('greatly, very much') is functioning as an intensifying adverb, not the unrelated adjective 大変 ('awful'); context picks the meaning. Note the を: 気にする takes the thing being worried about as a direct object, framing the worry as something one actively *does to* a topic.