Pip asks Biddy to educate Joe as his prospects now seem to change. Biddy instead, rebukes him for that. They almost start to fight. Why would you think Biddy could not like the idea at all?

Biddy knows that Pip is still stuck in his illusion of moving up in the world. Biddy knows that this is an illusion, especially for someone like Joe. She knows they are simple folk but are at least content. She refuses to let the poison of Pip's world infect her new husband and home.