Complex sentence: Sansa appears to crumble under the pressure of the situation, admitting her true identity to the group, but eventually corroborates Petyr's story, and convinces them of his innocence.
Split into simpler sentences: Sansa appears to crumble under the pressure of the situation, admitting her true identity to the group. At the end, however, Sansa corroborates Petyr's story, and convinces them of his innocence.