She passed the test at the expense of her friendships.
Literal
She [topic-は] friendships [object-を] sacrificing that test [to-に] passed.
犠牲にして ('sacrificing') uses the noun 犠牲 (ぎせい, 'sacrifice') as a suru-verb — 犠牲にする means 'to sacrifice X for Y.' 友達付き合い ('friendships, social relationships with friends') is the thing sacrificed. 合格した (ごうかくした, 'passed') is the standard exam-passing verb.