I believe that Wallis felt that if David did not abdicate that all would "come around" to her/their way of thinking. She could not conceive the situation where a "King" could be dictated to by parliament and the people. Least of all that his wish to make her his Queen could be thwarted.
As for the Queen Mother blaming Wallis..... she did. But on a purely personal level. We tend to forget that David was a dashing, debonaire batchelor who was also a beloved brother, brother-in-law and uncle!
Wallis took him away from his family and his throne, and, in the eyes of the Queen Mother, thrust her beloved husband into a role he had never been prepared for, and effectively removed her daughter from her and turned her into "The Heir". In short, their small, close-knit family (David included) was destroyed forever.
As for Wallis herself? Well, in those days men did not bring their mistresses to the family dinner table. And, like it or not, Wallis was not the innocent (virgin?) they were all expecting to join their family as future Queen.
The Queen Mother and Wallis obviously met, but they were never friends or contemporaries. I doubt they gave each other much thought at all as they had nothing in common.
Fate dealt a hand that both (for love) played out in anger, enmity and probably not a little regret.
