Karel's mother (and Marketa's mother-in-law) is pretty much a walking stereotype. When the couple are first married, they can hardly stand to spend time around her because she wants to be all up in their business, all of the time. And she wants to be critical of it, too.
But as she ages, and as Karel and Marketa come to see that she's becoming fragile, the two forget how much she drove them crazy. As Karel attempts to include Mama more in his life, he makes an astonishing discovery: "More time had passed than he had realized. Mama had relinquished the marshal's baton of her motherhood and gone into a different world" (II.2.7).
Mama don't care anymore. Karel's affairs (literally) don't concern her. She's dealing with an aging mind and body—including some seriously poor vision. Her poor eyesight not only spares her the sight of shenanigans she wouldn't want to know about, it also keeps her penned up in her isolation.
But that loneliness has become comfortable to her, and she's no longer interested in dealing with her son and daughter-in-law's issues.