Hi Nikhil,
Whatever I have posted on this thread is on the basis of what I understood from what you posted originally.
Since you said that you are in the 30% tax slab and your sister does not have any source of income.
Also that you wish to transfer Rs. 30,000/- every month to her which would be invested by her in FD on which she would be earning interest income.
So the initial impression one gets is that you are using her basic exemption limit to earn tax free FD interest income.
Further you also stated that you intend to submit Form 15G so that no TDS is deducted and there would be no requirement to file her Income Tax Return as her income will not exceed the basic exemption limit.
This led me to believe that this wouldn't be proper and the Interest income would be clubbed once the IT Department gets a whiff as this would be considered as tax avoidance or tax evasion.
However since you have now clarified that you do not intend to use the gifed money and it's a genuine gift then that is allowed and then there would not be any question of clubbing or benami.
Thank you