Daughter steals complete set of China and Sterling silver from elderly Mom. What should be done?

How awful. Yes, you need to find out if these items are willed to your SIL. If not, your husband should call his sister and demand that these items be returned immediately and if they are not, he should call the police and file theft charges. He should also get a restraining order against his sister and boyfriend so that they can no longer visit mom unsupervised. Unfortunately, this will permanently destroy his relationship with his sister.

They took all these things while she was sleeping!

I wouldn't hesitate to call the police.

Your husband needs to first find out if these items were going to her in the will anyway, if not then HE NEEDS TO GET ON THE PHONE AND TELL SAID SISTER THAT IF EVERYTHING IS NOT RETURNED TO MOMS HOUSE BY ______DATE, HE WILL BE FILING A LAWSUIT AGAINST HER.

SHE HAS COMMITTED THEFT!