Hello,
First, you need to calculate the capital gain on the sale of the property of your grandmother.
Since the property was acquired before 2001, you need to get the valuation of the property as on 1st April 2001, which will be considered as your cost of acquisition as on 1st April 2001. Which then will be indexed up to next year( sale year), which will become your indexed cost of acquisition.
This indexed cost will be reduced from the sale proceeds of Rs. 28 Lakhs, the resultant figure would be your grandmother's Capita Gain, and she would be liable to tax on this amount only.
Now to get an exemption from this capital gain, she needs to invest the Capital Gain amount(i.e. 28 Lakhs minus Indexed Cost) in another house property within the next 2/3 years of sale. Therefore the amount of Rs. 15 Lakhs to be invested in another flat would be available for exemption, and if the capital gain amount comes upto Rs, 15 Lakhs, your grandmother won't be liable to pay any tax on the capital gain.
I hope that this answer satisfies your requirements. For further understanding, you can contact us directly or take a phone consultation.
Regards,
CA Hunny Badlani