Roshni definitely has some majboori. Or else why would she hold a grudge for two years! That is not possible for her. She is the lead and they can't ruin her character so she is helpless for sure!
Simran does have something to do with it for sure! (my opinion) She probably exploded on Roshni asking her to leave and stuff. And her behavior today was weird, She said she would never forgive Roshni. Like what the hell even? Hope we get to know soon.