If a spouse decides to file for divorce while living separate and apart from the other spouse and then there is an attempt of a reconciliation where the spouses begin cohabitating with each other after the dissoultion petition has been filed but before a final decree of dissolution or before the dismissal of the petition for dissolution, the cohabitation has no effect at all concerning the desire for divorce.If your sister filed for a marital dissolution and then decided to live with her spouse the living with the spouse pending the dissolution petition has no effect upon it at all. There have been circumstances where parties file their divorce proceeding and continue to live with each other during the time period where the divorce has not been finalized and after the divorce has been finalized. The result is that the marriage is deemed ended.