。
She might not like his attitude.
Literal
She [topic-は] his [genitive-の] attitude [subject-が] is-not-liking [perhaps-かもしれない].
好き ('like') is a na-adjective, so its negation is 好きでない (or more colloquially 好きじゃない) — the でない form is slightly stiffer/written. The disliked object takes が (typical for preference predicates). ~かもしれない expresses possibility ('might, may, perhaps'); attaches to plain forms. The whole sentence is a hedged opinion: not a firm claim, just a possibility floated.