Ice Queen and Thunder God

The Frost Giants had believed that they lost everything when Odin defeated them long ago, but a few years later, they were brought out of despair when their rulers' only child was born.

A certain Girl-Who-Lived had been reborn into something more than just a witch. She was reborn as a royal of the Frost Giants thanks to the Hallows. At a young age, she learns to run a kingdom, and helps her people from ruin by transforming her home into a proper and respectable society. Although that doesn't mean that she faces occasional opposition. She also takes an interest in Earth or Midguard as it's called in her new world. Then she's thrown into a new hero mission when she meets a unique group of mortals with powers and a certain thunder god.