Maybe she just feels pressured and she feels she has to save everyone because she's a hero
Not really. She feels entitled to a new and state of the art equipment just because she's 'the hero'. She thinks she can defeat everything just because she's supposed to be a hero. Above all, SHE WON'T EVEN COMPROMISE!
What, is she supposed to fall at the feet of the priest who has no issues if her companions have to sacrifice themselves for her? Ares pretty much ruined his first impression with that off-handed statement and he's been consistently condescending, never explaining things clearly to the hero. He's never tried to understand what the hero is going through, or what her companions' hangups are. They're a means to an end, no more. She's stressing about being the hero and winning because the alternative is to fall to despair at the thought of the imminent death of her and her companions. She didn't ask to be summoned, and with Ares constantly babying her she doesn't know the full extent of what she's dealing with.
And if the hero who is supposed to kill the demon king can't get state of the art equipment, who should? She's in a hostile, unfamiliar environment where everyone's hiding information from her - yeah, I wouldn't trust Ares either with that limited information. He's shady as hell.
Every single one of the hero party (excluding the dragon girl, at least she's got some sense). The magician is a prideful, overly coddled little princess who can't take critisism, the warrior is an uptight little girl weilding a sword that thinks she's so strong just because she trained with a sword since she's little and she's a child of an excellent swordsman. The 'hero' is the f*cking worst of the bunch. She's a hypocritical bitch that spouts being a hero, saving everyone, and feels like the title 'hero' would be the answer to EVERY DAMN THING. She feels entitled to everything for being 'the brave one' and it's f*cking annoying. She always stresses being the hero as if she's going to be instantly op, DISGUSTING. She's so weak yet act so strong, and despises being told the truth that SHE IS A F*CKING NEWBIE THAT KNOWS NOTHING. SHE CAN'T EVEN DEFEAT THE WEAKEST OF MONSTERS AND SHE THINK SHE CAN STAND UP AGAINST THE DEMON LORD. LITTLE GIRL, DO YOU THINK YOU'RE OFF TO FIGHT A SCARECROW OR SOMETHING? YOU'RE OFF TO FIGHT THE DEMON LORD, AN EXISTENCE THAT A SQUAD OF MORE EXPERIENCED AND MUCH MORE STRONGER PEOPLE THAN YOU CAN'T DEFEAT! GROW UP YOU F*UCKING EGOTISTICAL, HYPOCRITICAL, BRAINDEAD MONKEY!