What is the ruling of Islamic law on a wife remaining with her husband after he has repented from the sin of touching her sister with lust, given her desire for a divorce despite his remorse and repentance?

Enjoying the company of your wife's sister is a grave sin. However, Allah accepts the sincere repentance of a servant, which involves abandoning the sin, regretting it, and resolving not to return to it, while concealing one's sin and avoiding the causes of disobedience. If you repent truly, your wife has no right to demand a divorce because of this transgression, for "the one who repents from a sin is like one who committed no sin." Explain this to your wife, and if she insists on divorce, you have the right to refuse it. Allah will suffice you in what worries you if your repentance is sincere.