When did Mary Maloney regain consciousness of reality?
Mary Maloney regains her consciousness of reality when her husband tells her she is being abandoned. At the beginning, she is unwittingly sunk deep in unreality. She believes that her husband is true to her, and that they are part of a project that will go on serenely into the future:
She loved to luxuriate in the presence of this man, and to feel almost as a sunbather feels the sun -- that warm male glow that came out of him to her when they were alone together.
Then, when her husband returns home, he reveals himself as a monster -- the sort of person who would not only cheat on his wife but abandon her when she is pregnant and expect her to take it all in good part with the offer of a bit of money. This makes it starkly clear to Mary that her whole life has been built on a lie.
Desperate, Mary's first instinctive response is to clutch at the remnants of domesticity: "'I'll get the supper,' she managed to whisper, and this time he didn't stop her." It is only when this final effort is rejected ("Don't make supper for me. I'm going out.") that she reflexively lashes out at him and kills him, ironically with the very leg of lamb that was to have become his supper.
After the murder, her thinking is clear and her motivation is the same as it had been before: love. Only now, she has shifted the focus of her love to her unborn child and will do anything necessary to protect it.
Mary is six months pregnant so when her husband returns home and tells her that he is unhappy and is leaving her for another woman she falls into shock and out of reality. She allows her shock to carry her to the basement, retrieve the leg of lamb, and smash her husband's head in with it.
"The violence of the crash, the noise, the small table overturning, helped bring her out of shock. She came out slowly, feeling cold and surprised, and she stood for a while blinking at the body, still holding the ridiculous piece of meat tight with both hands."
It was the act of murdering him and seeing him fall that brings her around to the realization of what she's done. Her reaction is rather peculiar though because she seems to care very little for what she's done so it's difficult to say that she's conscious of reality at any point throughout the rest of the story. In fact, after the policemen finish eating the murder weapon she giggles which might lead the reader to believe that while she's no longer in shock, she might very well be out of touch with reality.