Complex sentence: The "Sister" in the title does not refer to being a nun, rather, a rank she had held as a nurse in the Australian Army and also a term for a senior RN (which Kenny was not).
Split into simpler sentences: The "Sister" in the title does not refer to being a nun but rather a rank she had held as a nurse in the Australian Army. It is also a term for a senior RN (which Kenny was not).