This tells the reader how deep her love for Macbeth is. But, taken together with the other speeches she has already made, it could be a look at her true character and her desire to be the wife of the thane and eventually king. Macbeth seems happy that he has received this news from the sources he cites, while Lady Macbeth worries that he is too weak to make it come true. It does not seem like she is someone who is looking out for the best interests of Macbeth, she is looking out for her own best interests. She just realizes that to get what she wants, she will have to bolster Macbeth to get it.
When Macbeth enters, she is his loving spouse and greets him with the titles he apparently has already been awarded, and tells him that he will also be the king soon. She is fawning in her praise, but it does seem genuine. It is difficult to detect any cunning in how she addresses him here. He is also doting as he calls her "My dearest love." The two seem to be in a heart-felt conference from the first and it is the conference of two people who are in love. Both seem sincere in their desire and liking for the other.
She seems to know Macbeth very well because she first asks when Duncan will leave, and when he says that the king will leave tomorrow, she says "O never shall sun that morrow see." She tells him straight out that Duncan is not going to survive to ride from their castle tomorrow. He knows that she is prepared to do all that she can to make sure that Macbeth becomes the king.
The next bit of conversation between the two is interesting though. She is worried about Macbeth's countenance; that he will give away what they are planning. Before she was worried that he was too weak to do what needed to be done, and now she is worried that he will give away their plans. It seems that they have planned before this time to make sure that the king died and that Macbeth was able to take his place. She tells him "Bear welcome in your eye, your hand, your tongue. Look like th' innocent flower,…" She wants him to project a look of innocence and well-meaning to the king. She wants to make sure that Duncan has no idea what is going to transpire. Of course her next line is that he should be as a snake in the grass -- unseen, but deadly. It seems again as if they had previously planned this in advance when she says "put this night's great business into my dispatch, which shall to all our nights and days to come…" She is the serpent in reality and he acknowledges this apparently, but tells her that they will talk about it later.
In the end, Lady Macbeth is still pleading with him to mind his countenance and present a welcoming face, while she tells him that she will take care of it all. By the words that are spoken, Macbeth and his Lady have a deep relationship. They trust each other and they are working toward the same goals. But, it also looks like she dominates the relationship in reality to get him what he wants and her what she wants through Macbeth. Some of her speech seems conniving, and though she loves Macbeth, he had better keep his eye on…