Hi, I don't know specific psychologists in the L.A. area; maybe start with your pediatrician for suggestions, or a major medical center like UCLA, or check with the California Psychological Association. Most states have psychological associations that can give you a short list of people in your area who work with teens and families. Then you'd want to ask the psychologist whether he/she works with anger issues, and whether he/she works with teens as well as parents. I find in most cases it is helpful to work on strategies with parents and the teenager. Parents and teens each may have ideas about possible anger triggers. In addition, many of the strategies involve parents and teens working together. The second half of my workbook on anger overload explains how to work together, for example, teaching your teen about other points of view, and how to use catch phrases to help your teen think before acting out her anger. Most teens cannot develop these skills alone.
Individual therapy can be helpful though when there are underlying problems, such as worries about family, friends, or school. Teens may want to address these concerns without you in the room. So ideally the therapist is able to assess the problem in the first couple of sessions, and then work with the family and/or the teenager.
The two diagnoses that are sometimes mistakenly used for teens who get angry are oppositional defiant disorder and bipolar disorder. Many teens who have anger overload are not usually defiant. They just have difficulty when they get really angry. Further, they do not usually have a mood disorder. For bipolar disorder there would be many other mood related symptoms besides anger overload. By the way it is not unusual that your daughter might think she has bipolar disorder after reading about it. Any of us may think we have a disorder when we first learn about it; we call this "medical students' disease" because when medical students are first learning about diseases they think they have them. When they get more experience they realize they don't!
All the best, Dr. Dave Gottlieb