Uh...Wow. Yeah, mostly the same sentiments as the other comments. This is the prince acting pretty shitty. I haven't read the novel, but it sounds like the smut scenes that got cut out in an incredibly poor choice would've made this at least a bit better.
As it stands, she has no agency over her future, he doesn't put any value on her consent, and there's manipulation/pressure from all sides to force her into this.
If I were her, I'd probably consider branding over the mark with a hot iron or something to destroy it? This puts the prince in a bad place, but...well, fuck him. It's her body, she was never told nor given a reason to treat the mark responsibly, and this is her way out.
Also, if an intact hymen is all that took for her to be disqualified as a consort, you'd think she could've broken it on her own in secret.