Complex sentence: After her son and daughter were born, she began writing in earnest: an omnivorous reader, from 1958 onwards she became a prolific and compulsive contributor to the Oxford English Dictionary and by 1986 had "carded" around 250,000 quotations.
Split into simpler sentences: After her son and daughter were born, she began writing in earnest. An omnivorous reader, from 1958 onwards she became a prolific and compulsive contributor to the Oxford English Dictionary and by 1986 had "carded" around 250,000 quotations.