Agutyar….
My late mother A”H, had the BEST advice for being a good mother in law:
KEEP YOUR MOUTH SHUT AND YOUR REFRIGERATOR OPEN.
When she died 2 years ago she had lived to see all of her children reach at least 40 years of marriage. Her daughters and sons in law adored her, she never interfered or offered an unasked for opinion. She was always there when she was needed, but never intrusive in our lives.