In the Name of the King: A Dungeon Siege Tale

In the previous war involving the Kingdom of Ehb, a three-year-old boy was found wandering the field of the Battle of Oxley Pass by the rancher Norick (Ron Perlman) and adopted by the town of Stonebridge. While Norick could be considered his stepfather, the child was cared for by the entire town, including the family of Basstian (Will Sanderson) and Solana (Claire Forlani). His identity unknown, the boy grew up to be known as Farmer (Jason Statham), married Solana, and was raising his first son Zeph (Colin Ford) when war suddenly struck again with a surprise attack by the Krug.
The adversary was a Magus-in-exile, Gallian (Ray Liotta), sadistic, megalomanical, and very powerful, influencing the normally primitive, almost animal-like Krug to take up arms, don armor, and fight against Ehb with a courage, intelligence, and ferocity that surprises all of the Kingdom's inhabitants. While King Konreid (Burt Reynolds), Commander Tarish (Brian J. White), and a significant proportion of Ehb's standing army surveys the damage at and seeks recruits from Stonebridge, the King's nephew Duke Fallow (Matthew Lillard) and Muriella (Leelee Sobieski) allow Gallian to infiltrate the castle. Muriella's father Merick (John Rhys-Davies), the King's Magus is with the King at Stonebridge, and takes the liberty to investigate the matter of Farmer's true identity.
Farmer's adopted name belies his leadership and combat abilities and, in defiance of the King, he convinces Stonebridge's civilian combatants to mount a rescue mission. Gallian, via an avatar, had killed Zeph and taken Solana and other inhabitants of Stonebridge prisoner. Farmer's rescue mission goes very badly, Gallian nearly kills him because of the threat he poses (a mechanic of Kings, Magi, and magical power in the movie's world.) Farmer kills several of Gallian's avatars and escapes execution with the help of Merick, who brings him before the King to reveal his true identity as Camden Konreid, the King's son, solving a major inheritance problem: Duke Fallow is selfish and immature, poor material for royalty even if he weren't in league with Gallian.
Muriella had betrayed Ehb and her father largely by accident: she fell in love with Gallian, who proceeded to deceive and train her, stealing her power. After she realized his dark nature, she breaks off their romance, and confesses to her father Merick, who finally has an answer to another problem of his: a growing imbalance of the magical power in Gallian's favour. To offset this, the normally reclusive nymphs of Sedgwick Forest, led by Elora (Kristanna Loken) side with Ehb against Gallian.
The King decides on a surprise attack against Gallian's advancing forces, and Duke Fallow, caught in his treachery, has only his personal guard remaining. Gallian seeks the blood of Farmer, who prevails, while Duke Fallow succeeds in mortally wounding the King, who dies after the forces of Ehb force Gallian to retreat. Farmer's brief battlefield coronation surprises everyone except Gallian, and he decides to press to the attack all the way to Gallian's keep the following day.
Farmer leads a small force consisting of Merick, Muriella, and Elora through mountains to Gallian's back door. The main force led by Tarish and escape efforts led by Norick and Basstian keep Gallian busy, even as he interrogates Solana. Gallian's magical sense for royal blood reveals to him that Solana is pregnant with Farmer's second child, and because of his preoccupation with this, she is able to join in the final battle between Gallian and Farmer's infiltration team. Elora is not able to enter, while Gallian kills Merick and defeats Muriella's magic; Solana and Farmer kill Gallian together. With his magical influence gone, Gallion's avatars vanish and the Krug immediately revert to their natural disposition, retreating from Tarish's hard-pressed forces. The movie ends with the royal couple, still in their peasants' clothes, happily reunited.

Question: Who had betrayed Ehb?
Answer: Muriella; Muriella