Describe Gregor Samsa's relationship with his mother before and after the change?

As The Metamorphosis abruptly begins with Gregor’s transformation, it is a bit difficult to discern exactly what his relationship with his mother was like prior to the transformation. We know that Gregor has, until this point, been the primary breadwinner for the family. His mother, like the rest of his family, was initially grateful for his financial assistance but has now come to expect it.

“They had become quite accustomed to it, both the family and Gregor as well. They took the money with thanks, and he happily surrendered it, but the special warmth was no longer present.” (Part I)

Despite this, Gregor’s mother appears to care about her son when the novella opens. Unaware that he has transformed into a giant bug, she gently reminds him not to be late in leaving for work. When his manager comes to inquire about why Gregor is not at work, his mother defends Gregor’s dedication to his job, demonstrating that she understands the degree to which he has sacrificed his personal life to provide for the family. When the manager becomes incensed at Gregor’s refusal to leave his room, his mother becomes very upset, exclaiming in tears, “...he could be seriously ill and we're making him suffer!” (Part I).
Once Gregor’s transformation is revealed, Ms. Samsa’s initial reaction is one of terror. In fact, when she first sees Gregor, she faints right on the spot. She struggles greatly between the love for her son and her disgust and fear of the new creature that has taken his place. This takes a large toll on her mental state and, as Grete becomes Gregor's primary caretaker, Ms. Samsa's role in the household diminishes. Despite this, Ms. Samsa refuses to totally write off Gregor and eventually demands to see him (against the wishes of Grete and Gregor’s father).

"Later, though, she had to be held back by force, which made her call out: "Let me go and see Gregor, he is my unfortunate son! Can't you understand I have to see him?" (Part II)

Though Gregor misses his mother, he fears that the sight of him would be difficult for her to handle and he understands why the family wants to keep her from him. Ultimately, his mother forces herself to take a small role in his care and even makes an effort to understand his feelings. For example, when Grete suggests removing the furniture from Gregor’s room to make space for his large body, his mother quietly worries that he might interpret this as a sign that the family has given up hope that he will regain his human form.

“...by taking the furniture away, won't it seem like we're showing that we've given up all hope of improvement and we're abandoning him to cope for himself? I think it'd be best to leave the room exactly the way it was before so that when Gregor comes back to us again he'll find everything unchanged…” (Part II)

As time goes by, Gregor’s family has become increasingly estranged from him, just as he has been increasingly alienated from his own humanity. When his mother glimpses him now, she (once again) faints in terror. This time, however, her reaction leads the family to turn on him. When Gregor eventually dies, his mother (like his father and sister) feels relief that the ordeal is over and is ready to move on with her life. Throughout the novel, we see that, though Ms. Samsa is not a bad person, she was never able to fully reconcile that the creature and Gregor were one in the same. She almost never addresses Gregor directly, preferring to talk about him as if he is not truly present, and she clearly hopes that her son may one day “return.” In the end, it is clear that her feelings of sorrow are for the son who she thinks has been long gone rather than for the death of a creature that she cannot recognize as human.