Can the religiously non-committing past of one's fiancée be forgotten, and what is the best solution for confronting these feelings?

Whoever strives for righteousness must adhere to truthfulness and sincerity, preserve the obligatory duties, avoid major sins, and strive to guard against minor sins, bearing in mind that shortcomings are inherent to human beings, as stated in the Hadith: "Be righteous, and you will not be able to encompass it [i.e., perfect righteousness]." Regarding the wife, her current state should be considered, and no attention should be paid to her past, for Allah forgives repentant sinners. It is recommended to be kind to those who do wrong and to forgive oppressors. Therefore, one must strive to teach the wife matters of her religion and seek Allah's help.