How can one act regarding the two bracelets to please Allah, given that the friend does not remember exchanging the necklace for the bracelet, nor does she possess the original necklace?

If it is impossible to annul the usurious contract, then you should consider the value of the two bracelets, the value of your necklace, and the amount you added. If the value of the two bracelets has increased, pay the increase to your friend, and there is no harm for you in benefiting from them. If their value has decreased, your friend must pay you the difference. Al-Kasani said: If the buyer sells a corrupt purchase, or gifts it, or gives it in charity, the right of annulment is void, and the buyer is liable for the value or its equivalent.