Salaam - How should a wife deal with a difficult mother‑in‑law?

Assalamu alaikum. My friend has been struggling with her mother‑in‑law and I wanted to know what Islam says about serving or dealing with a husband’s parents. Is a wife obliged to serve her mother‑in‑law no matter what? Her situation: her mother‑in‑law is extremely toxic and often disrespectful toward my friend and even toward my friend’s family. She tries to make my friend look bad in front of her son, always insists on having things her own way, and acts as if everything requires her permission. My friend has tolerated this silently for about six years - she never answers back or defends herself. Her husband rarely stands up for her because he doesn’t want conflict with his mother, so she’s mostly left to handle it alone. They currently live in a different country from the mother‑in‑law, but when they stayed with her for a month the MIL made life unbearable. She resents that my friend spends time with her own family. My friend works, manages the house, cares for everyone, yet the MIL keeps finding fault and berating her almost constantly. My friend is deeply hurt and fearful that if the MIL moves in permanently she’ll be traumatized for life. She really doesn’t want to live with her. Questions: in Islam, is a wife obligated to serve or live with a difficult mother‑in‑law? Is it wrong for her to not want to have her live with them? How should she make dua and what practical steps can she take? Please keep her in your duas - she’s a gentle person and doesn’t deserve this pain. Only Allah can help her. Any advice or supplications you can share would be appreciated.