Well actually he was cursed but they both were going to be put back in the mirror. So she went with him. The story ends with her telling the story to her baby brother thru the mirror. They can't age but they explore places thru the mirrors and the magical land that surrounds them. She tells stories to children and its sad that she doesn't age as she watched her mother, father and baby brother grow up and then you see her telling stories to a brood of her great grand nieces and nephews. They have steampunk technology now and she's now the keeper of peace and history. Through the mirror, she even says hello to her mermaid friends and their great grandchildren. She misses her family but with her prince, they are immortal and explores the world around them. One day they may get free, but for now, as long as there is magic, they are the keepers of stories and watch over the kingdom.... end
I think she's going to get paired up with Verite especially with how the story visually makes them look the same age.(yes I know that's for Sable not to get jealous) I believe Verite is going to be let out when Blanche is older so that when he can't hide his appearance it won't be weird. They're also making Verite and Blanche interact more as a duo with how they scheme and convine together about Abigal especially with how they similarly react to things. But that's just my theory/prediction (of course when the real prince show's up he's either going to be cartoonishly evil, downright creep, love rival because we all love a good love triangle or the less likely option that he's just a decent dude that wants to be friends)