She feels that she sinned from the moment that she failed to respond to an instinctive distrust of the man who claimed to be her husband. She feels led into sin by him and the fact that he genuinely loves her is a matter for further despair. Through his love he has betrayed her and led her even more deeply into sin. And so her love turns to hatred of the betrayer. Love has little chance of surviving against the intensity of her concern for her own purity and clarity of conscience. For her there can be none of the excuses that we might make: that she did not intend wrong-doing, that she was led into it, that it was not really her fault.
If Bertrande wants to cleanse herself of sin, she must cease to accept the role of wife. At first she tries to deal with this by begging her "husband" to leave her, but when he refuses, saying that it would confirm her in what he claims is her madness, she believes she is left with no other option than to accuse him of being an impostor.
When Bertrande sees that the result of her actions is a death sentence for the man she once loved, she is appalled. It is not what she intended or anticipated. She thought only of ridding herself of the man. Before the trial at Toulouse, she hesitates, whilst Martin's youngest sister, the housekeeper and even the priest try to persuade her to relent and withdraw her accusation. She is shaken, but she remains true to her Conviction that she must cease to live in sin, and she must declare the truth.