You (and me) just like her because she is smoking hot! Be it an ugly b*tch we all would be ranting about how he should just k*ll them all starting from here and how much of a witch she is acting like
You're assuming quite a bit about me.
I like the princess because she doesn't fit the usual motifs we see for characters in her position in Isekai titles - she's not a blank pretty face who's meant to fall hopelessly in love with the cheat-powered MC, bereft of any personality or narrative three-dimensional quality; and she's not a token passive moment of fan service that fills no other role within the story.
She's antagonistic toward a person who has lied to all of the leaders of her home, after they had all worked to bring him to their world to save them from an impending calamity.
And yes - the premise is already absurd; this is an isekai story depicting a character who wasted his life staying indoors, neglecting his physical self, and spent all his time playing games and fantasizing about "wouldn't it be cool if I could be the hero of my own story".
He's been given exactly what he wanted, and now he wants to run away. Sure, he didn't opt in. But he could have spoken up immediately; instead, he spent three days eating their food and taking advantage of their hospitality, intending to simply hide his secret before fleeing off into a place he knows nothing about.
From her position - what she's doing makes sense, in the context of this person being their presumed savior, only to discover he'd hidden the truth from them all, and planned to abandon them. They exist in a medieval-styled world where there are literal monsters that spell the doom of humanity; capital punishment for someone who would betray the Crown, and humans at large, isn't an outlandish concept.
And, she's taking charge and telling him herself. She didn't run to her father, she's proactively forcing the MC to follow the story and fake being the hero, and even taking it upon herself to see him trained and prepared for the task,
and joining him on the journey. That amount of agency
isn't all that common among these sorts of titles, for her role specifically, and that struck me from the outset here.
Beyond that - we're given in the 'teaser synopsis' that each member of this party will not be as they seem. So a princess who is
not a passive pushover pretty face, who is powerful and also willful in her own right, is novel enough within this trope-addled genre that I find myself giving her the time of day simply to see what becomes of her character.
Her being "smoking hot" doesn't factor into it, for me.