Without context, it’s hard to tell, but it’s clear she doesn’t mean looking herself up on google. It most likely means masturbating, but it could be a little less specific, and mean something like making googly eyes at yourself—in other words, just kind of being infatuated with yourself; a form of narcissism.
Marge is not the most tech-savvy person; rather old-fashioned in a lot of ways.
She also isn’t the most intellectual or philosophical/meta person, so I doubt it would be as abstract as @wundayatta speculates.
My money is on her thinking it was the new slang for solo sex.