The Janis Joplin-biopic sub-plot may allude to the fact that at one time two movies about Joplin really went into production in Hollywood at the same time. One was called "Pieces of Me" and was supposed to star Renée Zellweger. The other (called "The Gospel According to Janis Joplin") was supposed to be directed by Penelope Spheeris and either Pink or Zooey Deschanel were rumored to star. As of 2009, none of the movies were made and both seem to be shut down forever.
It's very plausible that Stewart would have become close enough work colleagues to Kofi Annan, during their work at the UN, that they would have discussed their personal lives, even after Kofi Annan left the UN.