What should a married woman do who regrets committing adultery, has two children, and seeks sincere repentance and a return to Allah? Will her repentance be accepted, how can she atone for her sin, and what is the expiation for adultery?

You have committed a great sin by betraying your husband's trust and committing indecency. This is from the manipulation of Satan, who began with compromises such as working in mixed-gender environments and interacting with non-mahram men. However, the door of repentance is open, and Allah's mercy is vast. Therefore, you must repent by completely severing your relationship with this person, leaving work in mixed-gender environments, not speaking to men except out of necessity and according to Islamic guidelines, and increasing your acts of seeking forgiveness (Istighfar) and good deeds that expiate sins. You must also conceal what happened from everyone, including your husband.