Are the kisses and embraces that took place between a woman and her husband, while awaiting a ruling on their Khul' divorce, and a man who is a stranger to her, considered marital infidelity, and what should she do for sincere repentance after feeling remorse and cutting off the relationship?

If your husband did not utter a divorce or khul’ (dissolution of marriage at the wife's instance) and the judge did not rule it, then you are still his wife, and it is not permissible for anyone to propose to you. What transpired between you and the suitor, who is a stranger to you, is forbidden. However, your sincere repentance erases the effect of the sin. With sincere repentance—by desisting from the sin, regretting it, and resolving not to return to it—Allah replaces evil deeds with good ones.