She showed us the snapshots she took during her trip.
Literal
She [topic-は] trip-during [in-に] took snapshots [object-を] showed-for-us.
旅行中に撮ったスナップ contains a relative clause modifying スナップ ('snapshots'). ~てくれた marks the showing as a favor done for the speaker/listener. スナップ is shortened from スナップ写真.