Contrary to other FLs, I think she portrays a more realistic symptoms of anxiety and PTSD.
As for her picking her fiancé over Theo, it's because she needs a marriage with him. A noble. Theo is not a noble from the kingdom, but from a different country. If she picked Theo over her fiancé, she wouldn't be able to reclaim her inheritance rights from her uncle. Also, she just simply can't "stand up for herself" because she has no leverage in the world because she's a woman, ex-convict, and has severe PTSD. If she said no to his offer, she'd be left trying to search for another noble husband, which again would be difficult because ex-convict and unsavory rumors. Another noble lady did offer to help her find a "more suitable" husband, but it's obvious they were just going to keep the inheritance rights away from her (because said noble lady works for FL's uncle). So her saying yes to his bat-crazy conditions is because it's the easiest way out for her despite her fear of it all.
Also, another reason why she wouldn't pick Theo is to save him from the unsavory rumors, as she said before: it's best that you don't get involved with me. She's just doing him a favor. Yes, she did think of picking Theo's brooch during the switch-aroo event, but I believe it's only because she had gotten a hint from him and wouldn't want to end up with a random man otherwise because she thought she wouldn't know what her fiancé put on the table.
I understand what you’re saying but this is like borderline victim shame we obviously see that she has PTSD anxiety, and that there’s more to the story than what we know I think that she’s protecting the ML because I think the father was a bad person or he did something to her and then he accidentally burned I think there’s a lot more to the story and you’re just putting everything on her shoulders without seeing the bigger picture or knowing exactly what’s happening. And she doesn’t have the means to protect herself in anyway she doesn’t have a family who’s gonna stand up for her and love her her uncle’s obviously tricking her. We see that she doesn’t have friends. We see how she’s treated in society in multiple situations she literally has no one. She has no money she has nothing. Reputation is tarnished. Theo is a person she cares about, but she can’t fully trust because obviously she has trust issues reasonably so and she doesn’t want to burden the one person who actually shows her genuine compassion.
I'm not victim shaming her for her circumstances or whatever she went through up to this point, but I AM shaming her for whatever she will go through in the FUTURE when the ML starts hurting her and she'd be portrayed as the victim then when she willingly and wholeheartedly agreed to it like it was nothing. Her relationship with the ML going forward is on her, not just on him. He told her explicitly what he'll do, showed her with his shitty actions, and she was just like yeah sure.. but somehow I know she'll be portrayed as the victim. As someone who actually went through it, seeing the author include it in the story and making the FL accept it so easily, yeah, that's insulting. Also, to each their own. Respect your opinion but this is mine.

I've seen weak FLs and dumb ones, but to reach a point where she gets stood up at a party, he arrives 3 hours late, sees some guy about to attack her, smiles at him and says hey I propose basically a partner swap tonight each lady will choose one of the men's items and basically pawns her off then whispers to her I hope you choose me.. and despite 2nd ML who tried to defend her from the guy who attacked her asking her to choose his item too, she's like naaah let me choose the guy who didn't defend me, stood me up, is okay with me choosing another guy, doesn't have balls, AND she asks him again to marry her and he replies with: I have a condition, I'M GONNA HURT YOU and make you bleed 10 times and she's just like oh sure?
Girl, fuck you. Fuck you to the moon and back, you don't get to be a victim in this. It's offensive to actual victims.