Sounds something like this guy
http://www.davidicke.com/
Honestly, I don't think your mom is truly mentally ill. I think she might need to talk to a psychiatrist but I don't think she's clinically delusional or needs anti-psychotics or anything. She sounds a lot like my mom. My mom never joined a cult but she believed every conspiracy, listened religiously to Coast-to-Coast. She taught my sister that the battle between God and Lucifer was really aliens and when my sister was older she took her to conventions where they could have their "alien auras" or past lives read.
In my experience she just really needed the attention. She needed to feel special and feeling like she knew all the conspiracies and was enlightened to the truth gave her that. Of course my mom was also pretty messed up and not nice to her family and when we didn't give her the attention she needed she lashed out, so I washed my hands of the whole thing and I really don't speak to her anymore. I don't know if you want to do that with your mom. Your mom might just be lonely and misguided.
My advice is to not involve yourself. Try to take your mom out and do things with her away from the crazies and maybe try to get her to therapy but for the love of Alien Jesus, do not try to sit there and argue with crazy. It will just get you angry and feed their frenzy that someone is actually paying attention to them.