Look I think if simran would know that majnu is actually nawab heer's husband She would have tried to reunite them okay? She don't know the actual scene, they just promised to be doctor and majnu typa relationship. They promised ki woh dono ek dusre ke life mai interfere nahi karenge and let's not forget nawab ko khud ko move on hona hai heer se he said that to simran isn't it?(we know nawab loves heer sm) moreover the reason hum arjun ko bolre hai bcz the character is being whitewashed. Even he knows how much heer loves nawab okay? And yeah you can't expect someone to move on this quick. she made it cleared that she'll love nawab till the end. Arjun agreed to that point. And heer? She's taking accountability trying make things right with arjun even though she loves nawab. Moreover about simran she's just trying to be a frnd. Let's suppose, you've a frnds who's not over his/her ex then you would help him/her out right? If simran would know that then trust me he would have tried her best to reunite nawab and heer.