The way how she is portrait, her emotions going against FL in tactful way, reason behind it make her truthful. I can't imagine that in real life in the same situation with the same history accept FL easily. Her pride was already shattered, she heard only one convey between stupid husband and his guard she could not know what else was said also that FL and ML relationship would fulfill wish of her husband and as a reason in some way to mock her own marriage that would be unnatural if she would just say oh well let it be a special that there are other options as well.
As a person from country where church for long time had authority I just don't feel good about romance between priests and sister. She become sister to save herself but he I suppose got a call from God that means he is weak in his faith or is like priests during medieval - who chose church only to get power or money.