AITA for telling my sister her add-on "gift" can't look anything like my "gift"?

AITA for wanting exclusive rights to the gift I gave my mother for her birthday?<br><br>Our mother's birthday was last week and our family is (by requirement) supposed to give her a family heirloom or a family made pièce de résistance (jewelry, dress, necklace, scarf, etc.). I'm a jeweler, so I made her a beautiful platinum ring I designed as a child. Because I'm the youngest, my sister made sure to copy my design every year to gift our mother so it wasn't like she was "copying" me. This year, she went full on and asked to see the ring before I gave it to my mother. I showed her on the condition that she can't make a replica. I showed it to her. She did it again, and gave an exact replica with an "added" diamond.<br><br><br>I was so mad, I told her she was "a thief" for stealing my work for years, in front of everyone. She got mad, I got mad, and we got into an argument. Other family members were shocked as I don't usually speak like that. All family members are on my sister's side saying I went overboard and shouldn't have accused her of theft for "copying" my work.