Why does Mildred need help when Montag gets home?

In Part 1 of Ray Bradbury's Fahrenheit 451, when Montag gets home after meeting Clarisse for the first time, he finds that his wife, Mildred, is lying motionless in bed. While the narration specifically notes that Mildred is laid out "uncovered and cold, like a body displayed on the lid of a tomb," at first Montag thinks that his wife is just asleep as usual. Then he finds a "small crystal bottle of sleeping-tablets which earlier today had been filled with thirty capsules and which now lay uncapped and empty in the light of the tiny flare." Mildred has overdosed on sleeping pills and needs to have her stomach pumped in order to survive. Montag calls the emergency hospital, and two men come with two machines, one that pumps the stomach, and one that simultaneously empties the body of blood and fills it with "fresh blood and serum". 
The next day, Mildred denies having taken the pills when Montag confronts her about it, saying "What would I want to go and do a silly thing like that for?" She acts as if she doesn't remember anything from the night before, but we as readers know that the overdose probably wasn't an accident.