Is she the youngest in the family, could any of her sisters done it as you say she is interested in their body parts, and she is copying, it sounds like a game and nothing to be worried about, perhaps dont make any issue of it just be aware, doesnt sound like a big enough problem to go to the Doctor but if you are very concerned it wont hurt..
I agree with the first reply - the first line of defense is to contact your daughter's physician. If a psychologist or other specialist is required, he/she will be able to give you a referral. All the best .....
Im not sure about girls, but i know young boys can often be curious about their body parts. Has she actually said anything to elude to sexual conduct? Or is she just acting silly and showing her private parts?
Two totally different things, but its good that you are conserned. Maybe talk to her physician first (doctor) and see what he/she has to say before you resort to a therapist or psychologist.