What happens in the dream Miranda has about her deceased friend Becky?

Miranda dreams that her deceased friend Becky denies her entry into heaven. She is told that she is not good enough to be dead. The implication is that Megan will die because she is a good enough person to give up her food for others. Miranda will survive because she is selfish. Miranda understands that selfishness is an essential survival instinct, and that she needs to be selfish now more than ever. However, her dreams show clearly that she feels a lot of guilt because of this need to be selfish.