Why do Connie and her mother clash?

Connie's mother has a tendency to compare Connie to her older sister, June, and that comparison seems to manifest with Connie being considered inferior.  In the story's first paragraph, Connie's mother asks why Connie cannot keep her room clean like June does, and why she uses stinky hair spray even though June does not.
Connie's vanity is also a sore spot between mother and daughter.  Connie is fond of looking at herself in the mirror, and her mother criticizes her for it, asking "you think you're so pretty?" Connie believes that her mother is jealous of her beauty because she was once beautiful but "now her looks were gone."
On the fateful day of her aunt's barbecue, Connie opts to stay home and wash her hair to let it dry in the sun all day.  When she rolls her eyes at her mother in response to the invitation to go to the barbecue, her mother sharply responds, "stay home alone, then."
Generally speaking, Connie is a typically rebellious teenager who is testing boundaries, and her mother is a parent struggling with the transition.