。
She came to dislike an old friend.
Literal
She [topic-は] old friend [object-を] disliked.
古い友人 means 'an old friend' in the sense of a friend of long acquaintance, not an aged one — 古い paired with people normally implies length of relationship rather than chronological age. 嫌う is the verb form of the more familiar na-adjective 嫌い ('disliked'). In conversation, learners more often hear 嫌いになる ('come to dislike') or just 嫌い (current state); the active verb form 嫌った comes off as somewhat literary or biographical, suggesting a deliberate turning-against rather than a passive feeling.