To have committed pornea, you would have had to actually manipulate the other person's genitalia or engage in sex relations. I don't see how cyber-sex falls into that category, since the person stimulates him/herself.
In a Question From Readers a few years back, a guy wrote in that his wife had admitted to fantasizing about another guy. He asked if he could divorce her on the grounds of fornication. The answer given was no, since no actual sex had taken place. I wish I could remember which issue of the WT that was, but offhand I cannot recall; I only recall that it may have been written about 5-7 years ago, but maybe more.