At this point you are just making it easier for her....she gets to stay home(when she wants), Gets to stay(have sex with)her boyfriend(when she wants)and still has you as just a friend now. So for as cheater it all worked out better than she hoped it could.

My suggestion is stop being her friend...she really is a true friend!! Have you exposed this to mutual friends?? I don't think niceing a wayward who is still seeing/having sex with the OM actually works. Well it works for the cheater and the OM!!