What is the ruling of the Sharia on dealing with the husband's mother who invades the wife's privacy, divulges the secrets of her home, incites the husband against her, and harms the child, despite the husband spending on her?

A wife has the right to independent housing, and her husband is not permitted to house his mother and brother with her without her consent, as this infringes upon her right and violates the agreed-upon condition. Likewise, the husband's brother is not permitted to enter upon his brother's wife or be in seclusion with her. The wife's mother is not permitted to enter the wife's bedroom or bring anyone into it without her permission, nor is she permitted to treat the child in a way that harms him.

The wife should ask her husband to rectify the situation, and she has the right to ask him to remove his mother and brother from her dwelling. If he does not comply, she has the right to leave his house and return to her family. If he does not rectify the situation after her return, she may seek a divorce.

As for the husband's mother asking people for money while she is self-sufficient, this is forbidden. The wife must advise her and teach her the حرمة (prohibition) of that.