What is the relationship between Macbeth and Lady Macbeth like after Act 2?
The close relationship that existed between Macbeth and his wife before they committed the murder of their sovereign appears to have been badly damaged as a result of that unspeakable and irreparable deed. In Act III, Scene 2, Lady Macbeth describes what is happening to them.
How now, my lord! Why do you keep alone,
Of sorriest fancies your companions making,
Using those thoughts which should indeed have died
With them they think on? Things without all remedy
Should be without regard. What's done is done.
Macbeth is keeping away from everybody including his wife. He is doing so, as his wife tells him and the audience, because he bitterly regrets killing Duncan. He is torn by feelings of guilt, remorse, shame, and fear for the loss of his soul. He doesn't want to see his wife because she would only remind him of what they both did. And she apparently has not gone looking for him because she knows he will have to go through a period of mourning in seclusion. She herself is not especially remorseful, but she has discovered that there is not the satisfaction that she expected in fulfulling her wish to become queen.
Lady Macbeth will appear with her husband in Scene 4 of Act III, during which they are mostly hostile to each other. After that she will disappear until the last act of the play. She is all alone in her sleepwalking scene in Act V, Scene 1. When Seaton tells him the queen is dead, Macbeth simply says:
She should have died hereafter;
There would have been a time for such a word. V.5