This sounds like a criminal issue. Perhaps a landlord-tenant issue as well. Its not really a family law issue.
Best of luck to you.
This response is intended to be a general statement of law, should not be relied upon as legal advice and does not create an attorney/client relationship.
Tough situation. If she is honest, no problem. If she is dishonest, big problem. Send her a registered letter telling her you want your belongings and ask her for details on when you can pick them up. When she replies try to pick up your belongings. Save all correspondence. If this does not work, take her to small claims court.
This answer is offered for informational purposes only. It is not offered as, and does not constitute, legal advice. Laws vary widely from state to state. You should rely only on the advice given to you during a personal consultation by a local attorney who is thoroughly familiar with state laws and the area of practice in which your concern lies.