Logically join the dotted lines. The plastic surgery track was preplanned(not sure but analyse it). Firstly, most of the original cast moved out. It has relatively become a new show now.
Happy's plan was to make RV confess his deeds- fighting the wrong case against Rocky knowing Ranveer is the culprit/ pushing Anaya/ assaulting Rocky- but not to fake her own death. She didn't even need to marry RV to get his confession. The plan was to get RV punished, not to punish herself and her whole family. RV would anyway be hanged for killing Anaya.
HAPPY would anyway have to return to Amritsar and would be questioned and ultimately get trapped in her own plan. So that nobody recognizes her, she has to undergo plastic surgery.
Don't know about Jasmin's decision of quitting, is it true that she's quitting because of the kid track or the story demanded Happy's plastic surgery as the story took that turn only. Jasmin played the role of a surrogate in Dil se dil tak. She was shown pregnant and talking to her baby most of the times. So that cannot be the reason. I may be wrong but the story is gone for a toss. The only reason to bear up with this is Ansh now. As much as I want him to quit as he's binding me to this show, I still want him to stay as it's his first show so he shouldn't take any such decision that may affect his career. All the best to Jas but nobody will be able to recreate the magic of AnshMin other than them.