Wow, imagine coming to a residence of a girl child, threatening her and then scamming her to spend even more money. NO wonder they're treated like criminals there, it begs the question who's the villain here?
Seeing that panel with her crying reminded me that she is genuinely just a kid. Somebody needs to kick her parents in the rear and make them actually raise their daughter instead of letting the servants do it while listening to her every command.
Why the heck does she feel like she needs to be offended for the guy's sake? She seen already that the MC and her crush have a friendly relationship so why antagonise his friend and for what, just to impress him that you are wealthy?
I heard that in the novel (secondary source so I'm not sure if it's true)
she does win the mask and puts it on turning herself into a hulking monster which her crush had to defeat (just knocked out). In the end, her crush gave the mask to the MC as he deem the MC the only one who could keep it safe being a relic user and all.
He could just have lied with something like "I don't NEED that thing. I wanted to buy that dangerous relic to seal it away, but that public declaration you did destroyed my plan. Now it'll go to auction for an absurd amount of money and it became a problem." and it would get the message across.