Victaria and her brother (the youngest children of the then head of House Greyjoy) were taken as wards by a Westerosi House after the War of the Split Stag in which the Iron Isles sided with Durran Baratheon (one of the only Baratheon Kings to have their support).
During the Tourney of Longtable Ser Colen Baratheon was killed by a mystery knight during a melee. When King Orys II Baratheon forced the mystery knight to remove their helm it was discovered to be Victaria Greyjoy beneath.
"They say King Orys would have killed the knight in grey that day, would have struck the man down himself if he had not discovered a woman behind that grey shield. Victaria Greyjoy, a ward and remnant of Durran Baratheon’s war.” - Tanglefoot Ben to Tyrek Hill