It's in His Kiss: The 2nd Epilogue

What happened to the diamonds????

If you’ve read It’s in His Kiss, you want to know. Don’t miss this charming and passionate addendum, in which Gareth proves that some things get better with age, Hyacinth gains new respect for her mother (with a daughter like Isabella she’d have to, wouldn’t she?), and everyone learns that while diamonds are lovely, sometimes tenacity is a girl’s best friend.