Macbeth and Lady Macbeth do rely on each other in different ways.
First of all, both of them benefit from each other in the murder of Duncan (mutualism). They are mutually helped, because Lady Macbeth cannot kill Duncan herself and Macbeth would not have the guts without her pushing him.
I laid their daggers ready;
He could not miss ‘em. Had he not resembled
My father as he slept, I had done't. (Act 2, Scene 2, p. 29)
Lady Macbeth needs Macbeth to kill Duncan, because she will benefit from his rise to king (commenalism). Since she is a woman, she relies on her husband’s title. This often involves pressing Macbeth to do what she wants him to do, as in the case of Duncan’s murder.
However, Macbeth acts on Lady Macbeth like a parasite (parasitism). She helps him into office, but then he does not stay under her control. She is not able to keep him going in the right direction. It soon becomes clear that he is in a downward spiral, and she cannot do anything about it. She makes hurried excuses for him when he sees Banquo’s ghost at the banquet.
Sit, worthy friends; my lord is often thus,(65)
And hath been from his youth. (Act 3, Scene 4, p. 51)
Finally, Macbeth does benefit from Lady Macbeth’s death because she is the one other person who knows that he killed Duncan (predation). Since she is losing her faculties, it is much better for her to be dead than babbling.