A view to survivor´s guilt
I think she is a bit of an unreliable narrator, we only see her memories, her account... not saying she did anything bad... but that she carries (carried) a larger guilt than she should have, she is practically taking away all agency of the other adventurers, saying that SHE was responsible, when that was probably far from the truth.
Where the adventurers dumb, i would say they were too confident, not on her abilities, but on theirs, she even says so herself, nothing bellow insta kill can be healed, so they got cocky thinking they could endure a hit, so not dumb, just cocky, who hasn´t gone to the boss room unprepared and got their asses kicked.
And at the end she finally returns the agency back to the fighter, she will allow the fighter to fight (while abandoning a bit of her "kindness"), while also declaring herself as the de-facto "kill switch", if she says stop, all stops, going back to the trigger of her trauma, she was against some cocky adventurers, she said that they SHOULD run, that is the commitment the prince was addressing, now she is "if i say run, we run".
I liked it, pretty fun, also props for the prince having already a reflex of having something of him being cut