You can offer them a partial refund to pop into a jeweller's for a repair or a new safety chain.
Otherwise, you will have to accept the return, provide a return label and refund the buyer when you get the bracelet back.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
