Complex sentence: Feeling misunderstood and unloved after believing that her family have forgotten her 16th birthday, Diane runs away from home in January 1990 and joins the down-and-outs on the streets of London.
Split into simpler sentences: Feeling misunderstood and unloved after believing that her family have forgotten her 16th birthday, Diane runs away from home in January 1990. She joins the down-and-outs on the streets of London.