i mean she had the kid with her since birth when she moved away, and yet she never noticed he hummed when he ate food. she was the one who told wally off for doing it, and he said "u know i never know when im doing it" yet when he first met the kid, he noticed right away that he hummed whilst eating, but kassie didn't.
I can handle dead people, u kill a dog, i go crazy
Since kids can be noisy, anyone might chalk it up to "a kid just being a kid." Kassie had so many reasons to believe Roland was the father. If she noticed Sebastian having similar traits that Wally had, she could think it was a funny coincidence. Also, Kassie had a lot to deal with and may have been be more concerned with Sebastian's well-being, rather than comparing him to Wally.
I think that she probably forgot about Wally doing that. She moved after she got pregnant, so she was not around Wally for years. When Sebastian started doing the humming thing, she probably didn't even recall it, as it had to be at least 2 years later (8 months pregnant, and 1 year to eat that way).
~I am defying gravity, and soon I'll match them in renown...