。
She is reluctant to marry him.
Literal
She [topic-は] he [with-と] marry [nominalizer-の] [object-を] is-disliking.
嫌がる ('show displeasure / show reluctance') differs from 嫌う ('dislike'). The ~がる ending describes outwardly observable signs of an internal feeling, used in Japanese when reporting another's emotions — since you can't directly observe someone else's mind. Combined with ~ている, it expresses an ongoing visible state.