Is a mother sinful if she requests a divorce and her husband refuses to have intercourse with her, especially since she is living a very difficult marital life?

A wife must obey her husband in all matters that do not involve disobedience to Allah. His right over her is great, and the religious texts have clarified the importance of this. However, if the husband mistreats her, she has the right to seek divorce (talaq) or annulment (khula'). As for the husband, he must fear Allah concerning his wife, not oppress or humiliate her, and fulfill all her rights completely. He must also show protective jealousy over her and not leave her with a non-mahram man. Marriage is fundamentally based on affection and understanding, and spouses should overcome disagreements with wisdom and love, and each should advise the other without insult or humiliation.