is cyber sex cheating?

shes coming over on monday so im gonna talk to her then.
i cant go to the pub without her as i dont drive and its a long way from where i live.
she has asked him whats going on but he says nothing.
he says hes happy and the only problem they have is shes not, i couldnt belive it when she told me that, he doesnt understand that if in a partnership one of you isnt happy there IS a problem.