She helps Macbeth out by tricking him into killing the king. :P
The Prophecy says Macbeth will be king. Duncan is king. Macbeth cannot be king while Duncan is king. Duncan will not be king when he is dead. Therefore, make Duncan dead.
she wants to kill duncan so her husband can get his spot
The witches' prophecies all come true. Indeed Macbeth should beware Macduff because Macduff is the one who kills him, the one who is not of woman born. The forest of Birnam Wood (or part of it anyway) does travel to Dunsinane before the final battle.
A pretty tough lady.
Macbeth heads home to prepare his household for a royal visit. But he first sends a letter ahead, to give his wife the news of the witches' predictions. He shows up not too long after Lady Macbeth finishes reading his message [Act 1 Scene 5].
The letter of Macbeth was important to Lady Macbeth. It reinforced for her that the two worked together as a couple. Her husband confided in her, and respected and depended upon her advice and guidance. He didn't just tell her that they'd have the honor of King Duncan I as their house guest at Inverness Castle. He also updated her on his interactions with the three witches and their predictions of ever greater things for him on the job. Because she was warned in advance of the visit and of the predictions, she could prepare her household for her guest and her victims.
The prophecies in Act 1 set the events in motion by planting the seed of ambition in Macbeth's mind. The prophecies in Act 4 provide Macbeth with a false sense of security and invincibility, leading to his downfall as he blindly trusts in their deceptive promises. Both sets of prophecies manipulate Macbeth's actions and thoughts, ultimately contributing to his tragic fate.
The three witches predict that Macbeth will become the Thane of Cawdor and then the King of Scotland. They also predict that Banquo's descendants will inherit the throne, sparking Macbeth's ambition and actions to make the prophecies come true.
Lady Macbeth gives a signal to Macbeth to come and do the murder by ringing a bell. "The bell invites me", he says.
Macbeth and Lady Macbeth's castle at Inverness. (It's in Scotland on Loch Ness)
Macbeth attempts to act casual about the witches prophecies and lies to Banquo when he tells him he doesn't think about the prediction at all. In actuality, not only is it on his mind, but he is planning to kill Duncan to make the prophecy come true.
In the sleepwalking scene (Act V Scene 1) she goes back to bed when she dreams or imagines that she hears knocking at the gate. "To bed; to bed. There's knocking at the gate. Come, come, come, come, give me your hand. What's done cannot be undone. To be, to bed, to bed."