My sister is 15 and she has chest pains that only last about 5 minutes each time, they're very random, should we be concerned?

Probably not: Chest pains in adolescents in quite common, especially girls. Assuming she never had any developmental problems (i.e. Is fully active at school/recess/gym), doesn't reliably get the chest pains with exertion, and has a normal physical examination by her pediatrician there is probably nothing to worry about. If she hasn't had a physical in a while, she probably should.

Yes: Any chest should be study to find out what the reason?

No.: Chest pain can be common in teenagers and usually is not a sign of a serious issue. It may be due to inflammation of the cartilages that connect the ribs to the breastbone. It is a good idea to get this checked out so that the cause be determined.