What are the best abdominal exercises for a client who has had a TRAM flap procedure?

This client is several years post breast reconstruction. Her abdominal strength is very weak and I am concerned she will develop distention on the side where they took her abdominal Erectus muscle. She, obviously, can not do crunches, but she is also terrible at planks and other core exercises. Should I be focusing more on obliques and transverse training to strengthen her core?