。
She had made a doctor's appointment.
Literal
She [topic-は] doctor [with-に] consultation [of-の] appointment [object-を] had-made.
~してあった is the past form of ~してある — the resultative-state pattern with transitive verbs. してある signals a deliberate action whose result remains in place ('I made the appointment, and it is on the books'); してあった moves that whole resultative state into the past, leading the reader to expect something that follows ('she had it set up, and then...'). 診察 is the technical noun for a doctor's medical examination (consultation + checkup); 予約 is the general 'reservation/appointment.'