What should I do about my relationship with a girl I love, now that I’ve learned she is married and her husband is in prison, and I’ve had doubts about her past conduct, and I’ve lost trust in her?

The duty is to repent to Allah and sever ties with the woman, because she is married, and it is impermissible to propose to her or discuss marriage with her, for this is unanimously forbidden. As Ibn Kathir and Ibn Taymiyyah mentioned, married women are forbidden [to be proposed to], and it is not permissible to propose to them explicitly or by insinuation. This is an act of corrupting a woman against her husband, and it is among the most heinous sins.