Name one thing Mina did wrong.>"She tried to conquer Earth!"
Earth was presented to her as an unstable, chaotic, lawless society that would blindly follow any authority presented to them. At the time and within the context of the show, that's exactly how monsters were. She was shown an entire dimension of "Mewmans" that behave as "monsters", and found them needing to be culled. More than that, when it came to an election, instead of roiding out, she was willing to follow the rules of war instead of committing war crimes.>"She's clearly delusional!"
She's so aware of what's going on in the politics that she managed to stage an ambush at the Monster Temple's nursery and prevented Meteora from winning when Marco and Star were at their weakest. Whether or not you want to call it unintentional is irrelevant; Mina's actions paved the way for defeating Meteora, whereas Star in the same episode allowed Mewni's near-destruction to come to pass.>"She's not a strong fighter!"
She got one-shot by a cheap trick of magic no one had any idea Meteora could perform. Furthermore, Toffee used the same spell to one-shot the Magical High Commission, and in fact killed what's basically an aspect of god because of it. A spell like that has no defenses, and Mina cannot be penalized for losing to it.>"She's not a victim! She's a monster!"
She gave up her everything, no matter how little, small, and insignificant it was, because she wanted to serve her Queen and her people. In fact, she served to protect people who actively turned against their ruler, based on what we've just seen. That's selflessness by its purest definition.>"She wants to kill monsters!"