Well you're right in part because Karen would recognize MC's dick n' balls but MC is balls deep in Nikki's ass so you could make the case that because Karen was in shock that Nikki was having sex and that MC is so balls deep in Karen that she wouldn't immediately recognize MC. Also MC being faithful has unfornatly never happened. That's my biggest critique of this game. I know
HHUUKK is easily of the biggest Karen fans so I think that you should be able to stay faithful to Karen. We just gotta wait for the next update.