I know it's a drama but if I was Earn I will trusted P'Mor whom I have been dating for 3 years rather than her…
i think it's less about a lack of trust in lada than it is that fact that earn's mother is involved. of course earn's betrayal at the mention that lada was cheating led to her decision to break up, but lada's mother didn't only bring that up to sway her - she also made it about her mother's treatment. lada's mother makes her conditions clear: "IF you break up with lada, i promise to take great care of your mom." placed in a situation like that, earn's decision seems less irrational to me - it's also about making sure her mother will still get access to a good doctor and treatment plan.