It's more difficult than you think, imagine possessing a body (A) then loving someone (B) that has memories with the body(A) you possessed and they (B) share the same feelings with you, if you were to reveal that you are just some soul who took that person's body(A) how would person B feel? Betrayed, disgusted, scared, it might even ruin your relationship. So Ophelia is afraid of the risk of giving the magic circle that might expose her true identity which will lead to a doomed relationship. That's all, thanks! :3
She doesn't really have to explain her possessing Ophelia tho
Just say she was digging the sand and found it
Please just give ur husband the magic circle T_T