A) I have never ever seen her smile. She is always serious. She looks more like a robot than a human being. (Correta)
B) She Always is complaining about something. She seems to be never satisfied with anything.(Incorreta)
"She is always complaining... She never seems to be satisfied..."
C) Never I will understand her. (Incorreta)
"I will never understand her".
D) Don't you never ever say that again.(Incorreta - "double negative")
Don't you ever say that again.