In act 1, scene 5, Lady Macbeth reads a letter that her husband sent her. This reveals the strength of their relationship, because it shows that he trusts her enough to tell her about his encounter with the witches and their prophecies. A messenger informs her that the king will be arriving at their castle, and immediately after dismissing the messenger, Lady Macbeth proclaims
The raven himself is hoarse
That croaks the fatal entrance of Duncan
Under my battlements.
This shows us that she already plans to take matters into her own hands and murder Duncan rather than waiting to see if the prophecy will come true on its own. She shares this plan with her husband when he tells her that Duncan plans to leave the next day, and she replies:
Shall sun that morrow see!
She goes on to advise him to hide his true emotions, lest anyone suspect their plans:
Your face, my thane, is as a book where men
May read strange matters. To beguile the time,
Look like the time; bear welcome in your eye,
Your hand, your tongue: look like the innocent flower,
But be the serpent under't.
This scene is important because it shows us that Lady Macbeth is the planner and decision-maker in their marriage. She is bloodthirsty, and in later scenes when Macbeth has doubts, she must convince him to go through with the murder.
However, we see a shift after Macbeth has become king. He enjoys the power of wearing the crown, and although he fears losing it, he has gained a sort of confidence. He now makes plans and decisions on his own, without consulting his wife or even telling her. He meets with the murderers on his own, instructing them to kill Banquo and Fleance. In act 3, scene 2, when she asks him "what's to be done," he replies "be innocent of the knowledge." She tells him to be jovial during the feast, and he replies:
So shall I, love; and so, I pray, be you:
Let your remembrance apply to Banquo;
Present him eminence, both with eye and tongue:
Unsafe the while, that we
Must lave our honours in these flattering streams,
And make our faces vizards to our hearts,
Disguising what they are.
This is the advice that she had given him earlier, but now he gives it to her. This change reflects the broader change in their relationship. The reversal in who gives the advice tells us this, but the context also is important: Macbeth says this quote with specific reference to Banquo, who he knows will not be present, because he has ordered Banquo to be killed. Macbeth is no longer confiding in his wife and instead making important decisions on his own.