Police seem to think along the same lines too at this stage. Hence, according to the news Australian Police will be visiting her family in India soon. Looks like that means all avenues except the probability of organised murder have been exhausted.
Looking at the nature of the crime, the motive seems to have been to 'end' Prabha's life somehow (aiming the throat). Or else items would have been stolen or she'd have been sexually assaulted or the place of injury would be the chest or stomach.
Also, the fact that no trace whatsoever of the attacker has been left suggests it was a carefully calculated murder leaving no chance of being identified/tracked. If it was a random attack there's a pretty good chance that some careless clue would have been accidentally left behind.
All of this suggests to me she was targeted. By who, not evident yet.
http://indianexpress.com/article/in...tives-may-visit-india-to-meet-victims-family/