My Bff stole my Juicy necklace!?!!! GIRLS?

well my now EXfriend lives in my neighborhood and she sleptover at my house and later when she was walking home i ran to give her the beach towel she left at my house and i saw my Juicy couture necklace in her hand!! i was so upset i asked her where she got it and every question she was nervous and said "None of your buisness!" later i began to relize more stuff was missing (Jcouture perfume, chapstick, shirts, essie nailpolish) i later "madeup" with her to see if she had my stuff and it was all under the pillow except the necklace! i was furious and told her i wanted my stuff back and snatched it all in my purse and ran home. we were in a fight i blocked her from facebook ect... and cut off all connections to her. she was always really jealous of all the stuff i had compared to her stuff. and on a friends page i saw she had a picture with SOandSO with my necklace around her neck! i told her parents and they still denied it! and then her mom reported me to the deans for accusation. (iam really close to the deans because my mom works with the deans) and now it is said she has to buy me the same nacklace she stole from me! she even cried in the office!!!! She wont give it back at all!!! How do i get it back?!?! Btw i am 12.