Lila never died, she is living with Sia's identity.
Lila kills Sia.
The reasons being, There is no practical reason why one of the three x husbands would try to kill Lila after knowing that she has gotten the virus and anyway gonna die soon, as well according to the story they tried to kill her only because they were not able to put up with her so separation itself had satisfied the husbands. That eliminates them.
Sia the identical twin sister, the prescribed story stands alone without Sia being a character in it. The purpose for creating Sia is for Lila to swap her identity and to inherit the property in full possibly.
The party was just to bring all the characters in one place so that the authorities will have a handful of suspects.
My Creation -
I have 'G' and Lila as lovers. Since Lila and Sia share the inheritance if Sia dies Lila will automatically become the soul heir of the entire property. Money is the motive, G and lila planned to kill Sia. To execute the plan a stage was required which was the party that explains the 'suitable penitent' behaviour of G.The ploy of 'G' and Lila having the virus itself is fake, the public spat between these two was done just to publicize that they both have the virus so in the end nobody will suspect G for killing Lila. Also, Lila would have earned the sympathy of having killed with virus therefore no one would doubt on the possibility of Lila living in the guise of Sia. Lila successfully kills Sia in her house and bags the property and lives happily with 'G' ever after.
object from pringoo - http://www.pringoo.com/custom-designs/Snake7-cool~and~awesome~saying~and~design/did-14704/mid-3/ppid-79
for - blogadda (whodunnit)