Answer
(Fatwa: 1266/1038/B=1433)
Your mother has not yet given it to any of her daughters rather she has kept it with her. Yes she has kept it to give it to her daughters in their marriage, then merely by the intention of mother the girls shall not be the owner until it is not given in their possession. Hence the mother is the owner until she gives it in the possession of the daughters, so the zakah of those jewelleries shall be wajib on your mother each year. In future she can give the jewellery in small quantity in the possession of the daughters so that she will have not to pay huge zakah.
Note: The answer is correct, and zakah should be paid after passing a year as per the market price.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband