To be fair, it was Riftan who ordered them to stay silent about her miscarriage, so the fault is all his. Still, you have a point—Maxi deserves better than what she's gotten so far: a crap-ass family where her father and half-sister despise her, and an insufferable and selfish manchild of a husband who's never down to talk, but always down to fuck, right?
It does appear that Riftan ordered them to not say anything… but if I was the princess, since she is also a woman, I would have been honest with Maxi the moment she stopped going in and out of consciousness even at the risk of receiving Riftan’s ire.
Riftan is just a walking black flag at this point. No character development at all. Fucking horny dog. I started slowly hating his character a while back but now there’s absolutely no way for him to redeem himself even if he learns of Maxi’s background.
I read the novel, and the worst part about this is that he never EVER apologizes for being an asshole and hurting Maxi. Before Maxi leaves him for 3 years, the fucker harshly tells her to leave him, that he wouldn't wait for her and he'd forget all about her. Only after she finally leaves does the idiot dramatically race over to chase after her and break down in tears, claiming he lied about not waiting for her, as if saying then and there mattered at all. Riftan's a piece of shit.

So no one even had the courage to tell her she miscarried. That’s just fuck up. She deserved to know it the moment she woke up, no matter what her state was. It was her right. Even the princess or ruth didn’t tell her. I don’t care if they had reasons but no reason is justifiable enough to tell a mother, who wasn’t even aware that she is pregnant, that she miscarried, especially how everyone knew except her. That’s just cruelty.
At this point, i just want maxi to leave everyone and enjoy her life. No one deserves.