Complex sentence: When she was sixteen she started a two-year pre-nursing course at a technical college and when she was eighteen she trained and worked for four years as a state registered nurse (SRN) in the United Kingdom.
Split into simpler sentences: When she was 16, she started a two-year pre-nursing course at a technical college. At the age of 18, she trained and worked for four years as a state registered nurse (SRN) in the United Kingdom.