It depends on many things.

Do you have a written contract? If not, then you could be on shaky ground.

Did she actually purchase the display items? If not then they are on consignment and still belong to you, so she owes you money for the ones she sold.

Is there any way to identify your pieces as yours? If so, then you can probably take legal action, if your pockets are deep enough.

I would demand my monies owing and return of any stock she has, and cut all ties with her. I doubt she intends to manufacture herself; she probably wants to take the credit for your work. And has probably been doing so at the markets already.