。
I've come to like her.
Literal
I [topic-は] she [subject-が] like became.
The pattern [な-adjective] + になる ('become X') expresses a change of state. 好きになる = 'come to like, develop feelings for, fall in love with.' The adjective 好き takes its liked object with が; the final になる converts 'be liked' into 'become liked / come to like.'