Why is Wealtheow given to Hrothgar? What purpose does she serve in Hrothgars kingdom? How does she help Unferth?

Hrothgar’s arrogance toward Hymgod is supported by his military might—he could, if he wished wipe out the Helmings this very day. Instead, Hymgod proposes a treaty. He will give his sister to Hrothgar, thus linking their families and making the Helmings subservient to the Scyldings. Hymgod bestows upon his sister the new name “Wealtheow,” meaning “holy servant of common good.” Grendel watches as Wealtheow bestows her kindness upon the Scyldings, even though she is essentially a prisoner among them. He even sees her comfort Unferth in his isolation, declaring his previous humiliations by Grendel occurrences of the past, and bringing him back to his heroic self. Grendel also observes that Wealtheow is not actually happy to be among the Scyldings, only coming truly alive when her brother visits, but that she nonetheless looks upon Hrothgar with pity and compassion, while he is unaware of her looks.