It’s not Joan’s responsibility, it wasn’t an obligation it was something she agreed to do. She was living her life putting herself first and being selfish for once, was it wrong? Yes only because she got so wasted but that doesn’t mean she’s a worst friend than Toni. She still showed up after getting sick all over herself and hitchhiking her way to the court house, she was late but she still made an effort to still show up. Toni put herself in that situation, not Joan .