We first see Lady Macbeth reading the letter from her husband, which refers to her as "my dearest partner of greatness". Once she's finished reading it, she says
Glamis thou art, and Cawdor, and shalt be
What thou art promised.
Lady Macbeth is undoubtedly ambitious: though you could argue that she's ambitious only for her husband, rather than herself. Yet I think that perhaps the best interpretation is to say that she is ambitious on behalf of their partnership: self-obsessed and Macbeth-obsessed at the same time. She wants him to be king, but she wants to be queen too!
I think what follows in that scene gives pretty clear evidence that she's all too human. People sometimes interpret her as a sort of evil witch: yet if this was the case, there'd be no need for her to call on help from evil spirits:
Come, you spirits
That tend on mortal thoughts, unsex me here
And fill me, from the crown to the toe, top-full
Of direst cruelty!
This is a woman who needs to believe she has received cruelty from witches and evil spirit in order to win the crown. Is this - and her longing for greatness all too human? Yes.
As for her manipulativeness, just look at how she talks to Macbeth: and the way she persuades him by mentioning her dead baby ("I have given suck..."). She knows exactly which buttons to press.
Lady Macbeth becomes consumed with dark desires, such as greed, power, ambition and a lust for material possessions. One she discovers that her husband is destined to be king, she becomes single-minded in her quest to achieve this goal.
Nothing can stop her, she is like a runnaway freight train, steaming ahead at full speed, completely caught up in the acquisition of the goal. She does not consider the consequences, there is no morality involved in her decision making. She loses herself, her marriage, and eventually her life in the pursuit of power, position and wealth.
She loses touch with reality, in a sense, in pursuit of power. This is a very human expression, we can see it in the actions of dictators and corrupt politicians, in businessmen who don't consider the consequences, long-term, who sacrifice everything to obtain and maintan their power and wealth. Unfortunately, today, corruption and greed seem to drive the decisions of many people in positions of power.