Well indeed he story seems reasonable. In the media biz it is common that jewelery stores borrow jjewelery to actors in order to benefit from the free press. Obviously Mrs. Lohan received aleady a few times from jewellery stores such things. So she had choice to go to any store in order to get such a deal, so why should she steal?
On the other hand i would think that the jewellery shop owner who now accuses her of stealing is receiving now a lot of media attention and may exploit the fact Mrs.Lohan was in prison, because of drugs.
I would say she is the victim in this.