Why does Pip return to the forge in chapter 35? What does Biddy tell him regarding her future? What question does she ask that offends Pip?

Pip returns home to attend the funeral Mrs. Joe. Later, Biddy and Pip go for a walk and Pip asks what she will do now. She tells him she is going to open her own school. Biddy insinuates that Pip will not be returning soon as he promises. Pip leaves insulted.