I heard your sister is out of danger after the surgery — that's great news.

Literal

Younger-sister [subject-が] surgery-after crisis [object-を] escaped [hearsay-そうで], was-good [agreement-ね].

危機を脱する ('to get past the crisis, to be out of danger') is a set expression. ~そうで (hearsay + て-form) conveys 'I heard that' and leads into the speaker's reaction. よかったですね expresses shared relief.