。
She seems very full of herself.
Literal
She [topic-は] very think-rising-is [seems-ようだ].
思い上がる is a compound verb — 思い (the masu-stem of 思う, 'think') + 上がる ('rise up') — meaning 'to get conceited, to think too highly of oneself.' The image is of one's self-evaluation rising too high. ~ようだ adds 'it seems / it appears' based on the speaker's observation, hedging the judgment as inferred rather than asserted directly.