Desperation and delusion
The Lonely Passion is Judy's desperation for love and company. Without a family, her life has no meaning, and without a hope for a better future, she invents fantasies. The crux of the novel is her willingness to play along with those delusions because little by little, her bravery wanes and she is no longer able or willing to face the truth of her lonely life.
Alcoholism
Judy's loneliness drives her to drink, and to the extent that she feels lonely and desperate, she drinks. That means she usually drinks to ridiculous excess, because her suffering is extreme and unbearable for her. She often wakes up without a clue what she did the night before, and her overly religious and hypocritical housemates always make sure to humiliate her for her drunken rampages.
Sexual frustration
Although Bernie does have sex with the maid, it almost doesn't even count, because there's unresolved sexual tension between him and his own mother according to his Oedipal relationship to her. Otherwise, all the characters are lonely and grumpy, not to mention judgmental. They pretend to be offended, and so they never really connect. So most of the characters live with chronic sexual frustration that goes largely unresolved. This loneliness is a cruel addition to their already difficult lives in poverty.
