Sherwood Smith's Twice a Prince (with spoilers)
Sasha remains cautious and the hero keeps kicking himself (deservedly) for screwing up by keeping too many secrets when he met her. Not being a villain he lets her go (but sets one of his trusted friends to track and help her).
I love the fact that the friend/spy loses her soon after, due to weather and not any special skills by Sasha. I love it when she loses her way out of inexperience, is happy to be rescued from a storm at a military camp of the king and leaves in the morning without ever thinking about the consequences of a report about her showing up (she does use a false name, but her few treasures clearly show the connection to the old royal house). The villainous usurper also does not want to kill the heroine in this one (yay!), he wants her to marry his son and continues to want this (and to try to send his son to find her and woo her, as the prince's supposedly a real ladies' man).
The mother, increasingly seeing that the usurper keeps trying to seduce her and showing off to the court how happy she's living with him in his castle, manages to flee (with the help of resistance members whom she helped to escape capture in the last book) once it is clear that the captured resistance people can't be killed outright by the usurper (because their supporters manage to make him agree to a public trial, yay for legal technicalities of rule!). And being who she is and from the time she grew up in, she develops a plan of asking all women concerned (which is basically the married half of the country) to come with her in a big protest march to the usurper and ask him not to start a war (which is the second current plan of this guy).
We get great family interaction between the womanizing prince who is definitely not as he seems and his father, attempts at breaching the gap between them which both feel. This book has - as always with Smith - no clear cut evil villain, just people going wrong from various reasons who disregard the chances of turning back (with the vague but looming threat of an attack from Norsunder always at the back).
There was a military game which actually was supposed to show off the prowess of the nephew of the usurper's right hand man (who really is hoping/wanting to engineer an accident for the "imbecile" prince and make his nephew the next king). It all went wrong and the nephew is now after Sasha with his own corps of cadets, rethinking all the manipulations he has done himself and being done to him by his uncle, especially when he does capture Sasha (who managed to lose track of time in her journey to try and release her father from a spell) and she points out that you don't send cadets off to capture a princess with the clear order to "not tell anyone" and expect her to survive this.
It's the hero to the rescue and Sasha goes of on her own AGAIN, all of the major characters finally congregating at the place where Sasha's father is waiting to be released from his spell. Yes, there is a happy end of a sort, but the threat of Norsunder remains and the hero has to bear a personal loss.
I liked the hero more than Vidanric in Crown Duel when I first read that, because we are allowed into his head this time (we also get into the head of the right hand man and the usurper as well as Sasha's mum), so we had an impression not just of his deeds but of his feelings (since I've read A Stranger to Command, Vidanric remains my favourite Smith hero, apart from Inda). Sasha is more savy in some ways than Meliara was, simply because she grew up always on the look-out for danger and she's simply older. She's around 25, I believe.