She-hulk real name is Jennifer Walters , a cousin to Bruce Banner. There once an emergency blood transfusion from him when she was badly wounded where Bruce was a blood donor. After that she acquire a milder version of Hulk condition where she becomes a powerful green being but still retaining her personality. He can retain her intelligence and emotion control. When she is on enraged she will obtain a more stronger physical strength and her transformation is permanent.Source here
image sourceHer abilities includes superhuman strength, speed , durability and endurance. She has also a regeneration of healing factor. She has joined Avengers and Fantastic Four.Source here