OverKill (Rtte-Httyd)

Eria was your normal teenage viking girl, her family, respectable, her life easy, her love life, amazing.
ah, to be bethrothed to one brother but you love the other.

but things all change after Eria has to kill her first dragon. leaving both her lover and her self worth alone, now, 15 years later, they meet again, this time on different sides. Two side to the same coin.
(I don't see to much Httyd book now a days so :P)