Dr. Schaffer is Eric Foreman's boss while he had his own medical team at New York Mercy Hospital in the Season 4 episode 97 Seconds. She was portrayed by actress Kathleen York.
After quitting Princeton-Plainsboro Teaching Hospital, Foreman got a job similar to House's at New York Mercy, working with his own team of three fellows. However, on his first case the differential came down to infection and lymphoma. Foreman was sure it was lymphoma and that the patient needed radiation therapy as soon as possible. However, Schaffer was a by-the-book doctor and insisted Foreman rule out infection before giving the patient radiation because radiation would destroy the patient's immune system and allow the infection to run rampant. Foreman countered that if they waited to rule out infection, the lymphoma would have spread so far as to be untreatable. Dr. Shaffer was unswayed.
However, Foreman went behind Dr. Shaffer's back and took the patient to get radiation therapy himself. The patient improved quickly. Dr. Foreman was very pleased with himself the next day, but Dr. Shaffer fired him for going against protocol.