βtimeline info
β Kneel... before your Queen.β

Before it was too late, Hela was able to stifle her greed and bloodthirst for planetary conquest, soon after having stepped down and retiring as Odin's final Executioner. From there, she began focusing on leading Asgard's army, as well as learning everything it would take into becoming the future Queen. This meant strengthening her mind, magic and even her soul.
Hela knew that if she was patient enough and bided her time, the realms would eventually be hers and she would be able to continue conquering the realms beyond Yggdrasil.
Although she was not banished to Hel, the realm was still given to her to rule, along with keeping the right to travel to and from Asgard as she pleased. In time this allowed her to meet her brothers, as well as having a small hand in raising them. But when she was off to the other realm, Hela would be gone from months, to even decades in Hel, and always taking a battalion of the Einherjar with her.
She wasn't there when their mother was killed ( Frigga was her stepmother ), but she felt it when their father had passed, which was what brought her to her brothers immediately after. This is where Ragnarok would have happened, but since she had the loyalty of their people, they were able to embrace her as their new Queen.