I hope this message finds you well, present circumstances excluded. I am a licensed attorney with over a decade of practice experience. It is a pleasure to assist you today.
In California, who gets the ring depends on who broke-off the engagement. So, if your fiancee calls off the wedding, she has to give the ring back to you. The same is true - in California, at least - if you both agree to call it off.
As a general rule, you lose the ring if you cancel the engagement. An exception might come into play if you can show you had good reason to call off the engagement and so the cancellation was actually your fiancee's fault. For instance, if you cancel the wedding after discovering your fiancee was unfaithful to you, a court may order her to return the ring.
If she broke it off, then you get the ring. If she will not give it back, as long as it is worth less than $10,000, you can sue her in small claims court to have it returned.
Let me know if you have any other questions or comments.
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Best wishes going forward!