Who is Alisha from Me Talk Pretty One Day and what is their importance?

Alisha is a good friend of Sedaris's. She visits him once a year and always makes herself comfortable in a way that alleviates him from having to constantly entertain her. To Sedaris she is the perfect house guest, but she is also prone to being a bad judge of character and one year brings a new friend, Bonnie, with her to visit Sedaris in New York.