'fiend-like queen'. How true is this description of Lady Macbeth and what does Lady Macbeth add to Shakespeare's play?

Malcolm describes Macbeth and his wife as 'this dead butcher and his fiend-like queen'. How true is this description of Lady Macbeth and what does the character of Lady Macbeth add to Shakespeare's play? Shakespeare originally wrote 'Macbeth', for the existing king James I. The play was based on James I's relations as Shakespeare thought that this would please the king who would allow the theatre to remain open. Shakespeare comprised the play of witchcraft …

…depends on the audience's beliefs, which may vary. I think that Lady Macbeth adds a lot to 'Macbeth', her character is important to the script as it moves the plot along. If Lady Macbeth's character was not in the play Macbeth would have been found out earlier. Also, if her character had not been as aggressive towards Macbeth, the script wouldn't be as interesting or as bloody; this would loose the attention of the audience.