You can't lead Q&A if you're dating Chris (because he isn't involved with Q&A enough, and you don't go) or Malik (because you end up graduating on time, and Liz needs someone who will be around for a while).
You need to have Liz G. broach the topic with you (on February 16, March 4, or April 14). Then ensure you'll stick around (either fail your classes or switch majors to business by doing group study with Nate), do the safe sex skit, attend Q&A meetings, hang out a lot at Q&A, and then talk to Liz on April 29 when she brings it up again.
It should be straightforward at that point.
(The option you're talking about "Ask about leading Q&A" is to get James to lead Q&A, not you.)