There has been a lot of discussion about this on Reddit mostly fed by the theories that this is in some way an inside joke or reference to some deeper Stephen King universe item. This can mainly be attributed to the fact that the name Susan is very common in Stephen King stories, including being the name of Roland Deschain's true love, Susan Delgado, from The Dark Tower series.
Those familiar with SK's works will probably know that The Dark Tower serves as a sort of focal point that connects all of the Stephen King universe through alternate dimensions, or levels of the tower. Susan is one of the recurring themes through out SK novels that indicate a Dark Tower connection, others being references to the number 19, ka or destiny and comparing it to a wheel, a group that is brought together by destiny known as a ka-tet, etc.
All that said, it is possible that Annie's reference to the name Susan was an attempt at a Stephen King in joke, but it seems a bit of a stretch to me.