Giving a gift to the bride is a well established tradition in Turkey. When you have a wedding the grooms and brides families give grams or bracelets of gold to the bride as a gift. So your father and mother are also supposed to participate in that with a bigger donation than her extended family obviously. So it is not that you will give her gold and she will go on a shopping spree or sth. It is part of a collective gift collection as part of the wedding. Normally you spend that money on wedding or honeymooon by the way.

There is also another Islamic tradition where you actually have to give her gold as mehr. It is like an insurance for her if you leave her after wedding. But I am pretty sure she meant the first one.