In the humans that are around you, your wife comes first. If there are issues between your wife and your mother, do not disrespect your mother. Some people misinterpret “kindness to your mother” as obeying her even when she is wrong. Yes you serve her and be kind to her but when she is making a mistake you need to be a man and stand up to her and tell her kindly “mom this is wrong”.
Many women are suffering because of their mother in law, and their husbands will not stand up to her. The best of people can fall, the best of people can make mistakes. To correct them in a beautiful way is what is needed.
We have to fear Allah. Mothers are irreplaceable but they can replace their bad behaviour with good behaviour.