Defied: "I am jealous of her, but that doesn't mean I should try to hurt her or anything."
Discussed: "Didn't Sally try to poison you because you were her rival?" "Oh, that's just crazy talk."
Conversed: "Why does Sally envy Alice, anyway?"
Because Sally is so focused on her jealousy of Alice, she fails to develop her own talents enough to where she can achieve her own goals. As a result, she becomes a bitter failure while Alice goes on to great success.
Sally spends so much time sabotaging and thwarting Alice that her own skills are neglected. When Alice finally gives up and leaves her career in shambles, Sally is no better off.
In time, however, she learns to bury the hatchet with Alice and the two become friends and collaborators.
Sally then diverts all of her effort into improving her own skills and in time becomes Alice's equal, or at least becomes notable and celebrated in her own regard.
Played For Laughs: Sally's attempts on Alice's life fail hilariously.
Played For Drama: Sally succeeds at killing Alice, and she ends up getting arrested. The last shot of her is in jail: she's smiling.