Looking for this manga

Set in a medieval times where magic exists (I forgot if it was isekai or not), two kingdoms are at war with each other. FMC is really talented in magic (I think with fire) and is either called the Crimson Witch or Crimson Demon because she's a redhead too. She was forced to participate and kill people in the war against the enemy kingdom by her own kingdom (she's already tired af because her whole life was built in fighting and being used) and was given an magic choker / bracelet given by her 'fiance' the prince aka asshat who enchanted that if FMC ever betrayed him or go against him, she'll die. In the first chapter, she was in the battlefield until I think she blacked out? Collapsed? and the ML who's a knight or knight commander (I think he's either blonde or silver haired) from the enemy kingdom took her. ML kept her in his room? Where he shackled her with magic shackles so it nulls her magic, FMC didn't care that her magic was nulled but was surprised that she was alive and was thankful despite wanting to end herself as she was tired. Everyone in the ML's kingdom hates the FMC as she killed their loved ones and comrades ((CONTROLLED and FORCEFULLY against her will btw)) until one by one, they all find out the truth behind her story and they all pitied and cried for her then accepted her. FYI, FMC has been used as a weapon for so long that she is really naive and innocent when it's something outside of fighting.

Thank you in advance if you this! I appreciate it