Was she going to fence the violin?
I don’t know too many fences who would take a Stradivarius.
Theft of articles of art is often ordered by private collectors. Such collectors get an incredibly valuable item for under $100K. The item then, entirely invisible to the taxing authorities, remains in the family. Decades later it sails past the death tax and becomes inherited. Even later, once the trail is cold, the item may be sold at an auction. Note that such a violin is above any fiat currency because Antonio ain't making more of them. As a store of value they are better than gold and diamonds because you can always mine more of those.