Who is Joyce from Suttree and what is their importance?

Joyce is a prostitute who has a relationship with Suttree that lasts over a period of months. She leaves town frequently and makes a significant amount of money, which she gives to him. They live together in hotels and eventually in an apartment. This is a time when Suttree is very well-dressed and buys an expensive car, tasting a life of relative privilege again. However, Joyce wants to be loved and Suttree is not able to love her. She loses her mind, damages the car, tears up money and throws it out and has an emotional breakdown. As usual, Suttree walks away and returns to his houseboat.