Is a psychologist familiar with sex addiction?

Many are. If you are looking for help with this particular problem, i suggest you contact different mental health providers in your area and ask if they have expertise/experience with treating this problem.
FYI: "Sex Addiction" Not everyone considers "sex addiction" a useful diagnosis, in the first place. Read Dr. Marty Klein's thoughtful perspective on it: http://www.martyklein.com/why-sexual-addiction-is-not-a-useful-diagnosis-and-why-it-matters/ Suggest consulting w/ a sex-positive therapist to understand concerns you may have about yourself (or other person) in relation to compulsive sexual behavior.
Maybe. Familiarity with sex addiction depends less on the professional designation than on the professional's interest in the particular area. You might find competent professional help by attending a mutual support group and asking other recovering addicts about their experiences finding professional help.