How much of her body is a female allowed to expose when being examined by a male doctor or a non-Muslim female doctor?

Answer

According to the Shariah, a female may expose for medical treatment only the affected part. Exposure must be only to the degree of absolute need. [The manner described by you is haraam.] It is utterly shameless and not permissible for the patient and the doctor to engage in treatment which requires unnecessary exposure of bodily areas which will not be examined.