My girlfriend took my and I want it BACK!! what should i do?

My girlfriend took from me and I really need it back. Ive had it for a long time ever since my cousin gave it to me at our fifth grade camping trip. I really miss it and how it used to just sit on my lap. Except I wont miss how it used to leave its she dead skin all over my bath tub. Anyways my girlfriend took it and now she says shell never part with it. Its hers forever so she says. WHAT should I do. is the name of my pet iguana by the way.