Spoiler, I heard this from a friend so I some details might be inaccurate:
From what a friend told me, Maxi miscarried cause she got hurt and riftan blamed himself for it. Apparently he was miserable and thought it better to send maxi to the royal castle. Maybe he thought she blamed him, too, who knows. Also, Maxi and the princess become good friends. Thanks to her Maxi saw how to be bold and she even laughed out loud while dancing. But maxi was pretty miserable being send away and losing her child, especially since they talked about having children in the novel.
That's where her asshole of a father went after her again cause some rumors about her not being able to carry child or something reached her sister's potential partner (royal family) and he wanted her out of the castle and out of mind. He brought her back to her childhood home where he abused her.
Another spoiler: riftan found out about Maxi leaving the royal castle and went after her, where he learns the truth and sees her father abuse her.
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From what I read from other spoilers, if riften tells her to go back to the castle cus she had a miscarriage and she gets abused again I think ima cry like ima feel so bad for her