Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
This might sound a little complicated, but Capote's attitude toward Holly can be different than our reactions to her (and we think this is part of his talent). Some of us might not like her or feel any sympathy for her, but Capote seems to do both. He actually presents us with a lot of reasons to dislike Holly, but he's also careful to temper that with some information that probably elicits a sympathetic reaction to other parts of her life. For example, after she coldly criticizes the narrator's writing without any thought of how her words might hurt his feelings, we're soon introduced to Doc and he tells us the sad story of Holly and Fred's childhood:
"Well, you never saw a more pitiful something. Ribs sticking out everywhere, legs so puny they can't hardly stand, teeth wobbling so bad they can't chew mush. Story was: their mother died of the TB, and their papa done the same – and all the churren, a whole raft of 'em, they been sent off to live with different mean people. Now Lulamae and her brother, them two been living with some mean, no-count people a hundred miles east of Tulip. She had good cause to run off from that house." (9.18)
No matter what we might think of Holly as an adult (and some of us might use the term "adult" loosely when discussing her), it's pretty hard not to feel bad for a young child with no parents, who has no food to eat and no safe place to live. Capote doesn't gloss over her negative qualities, but he does present us with details that complicate these downfalls. We get a better idea of why she does whatever she must to survive, and there are enough of these types of details in the novel to suggest that Capote himself feels a good deal of sympathy for her as opposed to a desire to criticize his novel's heroine.