After a recent rewatch of the HBO TV series, Game of Thrones I realized that Eddard "Ned" Stark's mother, Lyarra Stark is never mentioned or shown during the course of the series [to date]. Not even in Bran's time traveling sequences!
In fact there is very little information about her on various Wikipedias and it seems her name was not even given until the publication of The World of Ice & Fire tie-in history book.
Now I can understand that perhaps she simply doesn't factor into the story, but George R. R. Martin tends to be a stickler for details and even in the books there isn't much, if anything about her.
My question is, is there any reason her character has been excluded? Has Martin ever publicly addressed this or have the HBO Showrunners?