She came back in the end, because at some point she figured out that he was the was the only man for her, and perhapes she figured out that she had AIDs, so she wanted to spend her remaining time with him. Not because he had money, but because he was a good guy. And that he loved her, and she loved him back.
Cruel? Think about it, she spent how many months with a group of black panthers. Do you think they were just really really nice guys and supported her drug habit? HELL NO, she was the BP clearing barrel. So while he was working his ass off she bangs every guy in town, he gets ahead in life and has a spare minute to drop in and share some aides.
Yeah it's friend zone until she needs him for something.... Maybe it WASN'T the money, OR the fact that she needed someone to take care of her because she had AIDS, but I'm sure those things didn't hurt. WHO ELSE WOULD TAKE CARE OF HER FOR FREE?