Amy's wild habits and self-harming behavior seems to stem from her unhealthy relationship with her father and loss of her mother. Her younger sister has a different relationship with their father and interpretation of their childhood experiences, which leaves her in a much healthier state when it comes to how she takes care of herself. The sisters remain close regardless of Amy's behavior because of their genuine affection for one another.
Even though the humor was on point throughout, the tension was very palpable in how her past was affecting her future happiness with the doctor. The mix of great one-liners and emotional depth leaves this as the comedy to contend with in 2015.