Ymir was given a second chance at life and she understood that but that gift she was given she had to return it to the warriors who she took it from.
Ymir understood that she had to return it and she lived her life the way she wanted to and met Historia and fell in love.
and her only regret was that she wasn't able to marry her.
Her leaving Historia was sad but it was going to happen sooner or later
With Historia she lived her life the the fullest and helped Historia re-take her name.
In conclusion Ymir supremacy 🛐