Pettigrew:

If you have been paying attention, Myrtle has also made the claim of Schizo, Jester, and Backwards Jester, among other things... It is hard to believe what she says. She could merely be trying to get us to kill her and waste a lynching to throw us off the trail of the Mafia.

Also, if you pay attention, she was trying to get a Mason to recruit her, now that we are certain we have Masons. It is stated in the roles that if a Mason tries to recruit a Mafia member, the Mason dies. Perhaps that is the reason she is claiming Cult. To kill off our Masons...