Lord of the Rings or The Hobbit?
Ironbite-I don't count the one I can't spell.
Background material to The Lord of the Rings. As I recall, there's a mention in the Appendices that's expanded upon in some of his other writings, where it's confirmed that her "torment" was in fact rape.
In 2509 Celebrían wife of Elrond was journeying to Lórien when she was waylaid in the Redhorn Pass, and her escort being scattered by the sudden assault of the Orcs, she was seized and carried off. She was pursued and rescued by Elladan and Elrohir, but not before she had suffered torment and had received a poisoned wound.
(Year is Third Age. She was traveling to Lórien from Rivendell since she was the daughter of Celeborn and Galadriel. A year later she passed over the Sea to Valinor.)