Katherine Mansfield makes it clear that female jealousy in "A Cup of Tea" comes from personal insecurity rather than simply desiring what others have.

Rosemary is an intelligent, rich, and lovely woman. However, at the beginning of the story, Mansfield says that she isn't exactly beautiful. Despite everything she has in her life, she doesn't have that one quality.

Because Rosemary is lacking beauty, she feels jealous when her husband compliments Miss Smith on her appearance. It makes her feel insecure to know that he recognizes something in the other woman that she herself does not possess. If Rosemary felt beautiful, she'd likely feel less jealous when her husband makes that comment.

She sends Miss Smith away after her husband says the woman is pretty. She feels upset and flustered at the thought that Miss Smith has something she doesn't—it makes her feel insecure. She then goes to her husband for reassurance, asking whether she, Rosemary, is pretty. The jealousy she felt as the result of insecurity can only be soothed by knowing that her husband finds her pretty as well.