。
She loves him all the more for his faults.
Literal
She [topic-は] him [at-に] faults [subject-が] exist [because-から] all-the-more him [object-を] is-loving.
かえって ('on the contrary, all the more, instead') marks a counter-expectation — 'despite faults, she loves him even more (rather than less, as one might expect).' The ~から marks the cause; the structure stages a paradox: faults that should make her love him less in fact intensify her love. に on 彼 marks where the faults reside (the location of the existence verb ある). A small philosophical note on the Japanese view of imperfection as endearing.