In the end, Ms Beatrice dramatically acted herself as nothing happend to her mind and pride, just to force herself neglect the fact that Maid Sophie had almost fully occupied Ser Edward from his body to his heart far earlier from the first meeting of Edward and Beatrice.
She could not admit or realize this fact proven by Sophie and Edward, at least, admit it to their face, for preventing self-suspicion of her in-fact "Noblesseoblige" and her in-fact questionable "True Love" to Edward.(I think)