What is Johnny's reaction when the nurse tells him that his mother is at the hospital to see him?

Readers are informed very early on in the book that Johnny's home life is not good and that his relationship with his parents is terrible. His father beats him, and his mother either ignores him completely or screams at him.

His father was always beating him up, and his mother ignored him, except when she was hacked off at something, and then you could hear her yelling at him clear down at our house.

Johnny's parents show no love for him, and that is confirmed again for readers in chapter 6. Dally, Johnny, and Ponyboy are all talking, and Dally is informing Johnny and Ponyboy of some recent news. Johnny asks if his parents have asked about him, and Dally flatly states that they have not. The news is not surprising, but Johnny is still hurt.

"My parents," Johnny repeated doggedly, "did they ask about me?"
"No," snapped Dally, "they didn't. Blast it, Johnny, what do they matter?"

Once Johnny is in the hospital, his mother does come and try to see him; however, Johnny knows that she isn't there for any kind of good reason. Johnny flatly denies his mother access to him. He tells the nurse that he does not want to see his mother. Johnny believes that she has only come to berate him for one reason or another.

"I said I don't want to see her." His voice was rising. "She's probably come to tell me about all the trouble I'm causing her and about how glad her and the old man'll be when I'm dead. Well, tell her to leave me alone. For once"—his voice broke—"for once just to leave me alone."

Johnny is so enraged and upset by the entire situation that he passes out.

Johnny has a terrible relationship with his callous mother and does not want to see her when she visits him in the hospital.
In chapter 8, Johnny Cade is lying incapacitated in his hospital bed when the nurse informs him that his mother has arrived to visit him. Johnny reacts by telling the nurse that he does not want to see her. Johnny mentions that his mother has probably come to visit him so that she can tell him how much trouble he is causing the family. Johnny then tells the nurse to tell his mother to leave him alone for once. As Pony and Two-Bit are leaving the hospital, they see Johnny's mother arguing with the nurse about her right to see her son. When she spots Pony and Two-Bit, she blames them for Johnny's injuries. Two-Bit responds by telling Johnny's mother,

No wonder he hates your guts (Hinton, 105).

Ponyboy feels sorry for Johnny and shoves Two-Bit along before he can cuss out Johnny's mother.