You need to decide what you want and *ask* for it. They may accept your offer, or they may make a counteroffer, or they may reject your offer. You are free to take them to small claims court.

Personally, I think that $250 is very cheap for a diamond bracelet (I mean, yes they look lovely, but they're not the best quality), so consider asking for equal trade-in value, and getting something smaller but of higher quality, like a pendant or earrings.

Just my two cents'.