That girl doesn't suck, she is actually more afraid of the other guys because they all have high status and have become obsessed with her, think yanderes, she is scared seeing as they just how casually destroyed someone else's life and isn't happy about that at all, but i guess it was a plot twist in the novel that the girl isn't evil at all, mostly scared, and she becomes friends with the other two.
Though the prince doesn't want to make her queen, he has more of a big plan to screw everyone over for power and get sympathy and love from everyone, particularly the public, so he plans to get a girl and call her his "true love" and then tragically kill her...yes, the other guys like her, but the prince just wants to make himself look like a romantic guy whose life becomes tragic to get sympathy, she's just there to die, she actually never even tried to seduce anyone despite what everyone else thought, this being a more comedic novel, she only almost dies but Anne-Sophia and Euphy save her life by casting healing magic as she was near death and expose the prince after he...well, stabbed her heart and planned to frame someone else.
Also, the girl you say sucks?
She's a lesbian and falls for an older maid(only something like 10 years older) of all things, i don't think she cares about power all that much.