Myrna used to bring up Lucas on her FB with some regularity, usually around his birthday, or when she felt like explaining to her friends how hard she has fought for the rights and dignity of the mentally ill. She made posts about phone calls from him, too, which may suggest that those did not happen with regularity.
I've included some representative examples below, with Lucas's face cropped out, because he is ugly.
In the first image above, Myrna states: "He has experienced family turning their backs on him because he is not perfect." This seems to be true of his brothers and father. It may be true of Myrna as well, but I'm not certain that the LA adventure or some event in its aftermath was the final straw.
Myrna hasn't had much to say about her "handsome" son on FB since 2019. To the extent that not mentioning someone by name on FB is an indication of alienation, this may represents a change in their relationship. Or perhaps she decided to stop discussing her son's problems in a public forum. While Myrna's new posts about "being done" with unappreciative people are obviously relevant to her relationship with Lucas, it isn't as if she was involved in his life and constantly shouting him out up until recently.