。
She was indifferent to politics.
Literal
She [topic-は] politics [regarding-には] indifferent was.
無関心 (むかんしん) means 'indifferent' or 'uninterested' — 無 (without) + 関心 (interest). 政治には uses に (toward) + は (contrastive) to mark politics as the specific topic of her indifference. The past tense だった suggests this was her past attitude.