when she was admitted in hospital how convenient of her to require treatment from Onir,she probabaly paid the doctors at Mumbai to request Cnir so she could be closer to her goal..and why is onir helping her,well i think he is being paid a handsome sum or he wants Purvi to lean on him after she lost her baby because just like Arjun is still in love with purvi so is she and a husband/wife must sense when his spouse is not in love with them...ovi probableycame across purvi's pregnancy test and thats when her plan kicked in...
thats just my take ...