Parveen is not normally injured in any accident or got attacked by a normal person.
Haiwaana used her magical powers to kill her .
So ,no doctor can cure her completely.
Who knows Tabeezi again find out that only ayaana can cure parveen completely .only ayaana's positive touch can nullify haiwaana's black magicšš.
P.s. this is just my guess ,there is no spoiler or anything of that sort .
I think that im very excited to see post separation episodes that's y creating scenarios abt situation in which roshan can meet