Her Mother In-law Wants To Move In Permanently ... She needs help

How many of you would not mind your mother In-law who just retired and is not sick or needing medical attention come and live with you and hubby permanently?!

My friend's mother Inlaw is planning to do this. My friend is not comfortable with it at all but has resigned her mind to it.

The mother Inlaw often visits them and spends weeks and months with them even though she does not get along with the wife. The wife told me the mama never wanted her first son to marry and would have preferred he continues to bear children outside wedlock. He had a child before marriage. They have children of theirs now.

Sincerely, I can't undastand the rationale behind a mother moving into her son's house without invitation or permission. Is it fair?

Note -she has a married daughter o. Is it not better for her to live with her daughter if her and her daughter in-law dont get along? This lady now has strong cause to believe the mama is out to break her home. Would she now be receptive to her coming to live with them permanently?