Complex sentence: As Countess Spencer, Raine was unpopular with her stepdaughter Lady Diana Spencer, who even went as far as to using the nickname Acid Raine when referring to her step-mother.
Split into simpler sentences: As Countess Spencer, Raine was unpopular with her stepdaughter Lady Diana Spencer. Even going as far as to use the nickname Acid Raine when referring to her step-mother.