Zakaat on gold for previous years

Kindly help by giving us the amount to be paid as Zakaat for the following jewellery (Kindly note that the owner never had any excess cash all these years, people would assist her financially; the jewellery was given to her as a gift in 1985, she now wishes to sell it in order to pay for the Zakaat of the past years). 21 crt bangles - 75.80 gr, 18 crt bangles - 66.90 gr, 18 crt broken gold - 116.50 gr. ( For my information I would like to know if the quantity/amount of gold will be reduced each year when calculating, as the lady never had any excess cash, and if she had to sell the jewellery to pay for the Zakaat then the quantity of gold on would decrease each year by 2.5 percent).