Complex sentence: In 1974, she began a lesbian affair with her own daughter, aged 16 at the time, but during a crisis of jealousy in 1978 she incited the girl to commit suicide.
Split into simpler sentences: In 1974, she began a lesbian affair with her own daughter, aged 16 at the time. Finally, during a crisis of jealousy, in 1978, she incited the girl to commit suicide.