Your question is the best thing I've read all day. Apparently it's referencing a literal cheeseburger.

According to this person (spoilers? I haven't read the book and it's unclear whether this info is revealed before or after the line in question),

>>!It turns out that Bree was a 15-16 year-old abused homeless runaway. Riley ("the hottest boy I had ever seen, tall and blond and perfect... And his voice was so gentle, so kind") offered to get her a burger. Bree figures she knows "what he would want in exchange," but she's eaten nothing but trash for two weeks, so small-scale prostitution it is.!<

Meyer has several editors, after all; small things might slip by but if "cheeseburger of pain" managed to escape notice as an unintended typo then several people are straight-up incompetent.