Why does Corrine isolate herself and begin drinking heavily in the novel, Valentine?

After her daughter Alice is grown and has moved away, Corrine is overwhelmed by shock when her husband, Potter, is diagnosed with brain cancer. She is even more furious when Potter refuses treatment. Not long before his prognosis is up, Potter kills himself. Reeling from the shock of Potter's absence, Corrine self-isolates and begins to drink heavily.