From the information I've read, you receive a duty exemption on household effects entering the country. However, personal effects, including jewelry, only get the standard customs exemption.

I would defiantly bring receipts of the items that are high value to show proof of purchase in the US. In the future if you plan on moving away from the US with high value personal items such as jewelry you should consider filling out CBP form 4457. This will show proof of purchase in the US. If you do not have receipts, try and bring any evidence that the items were purchased in the US. I would declare everything being brought in for transparency sake, its better to be up front about it; instead of not declaring the items to CBP.

The CBP website has some useful information about moving back to the US. You could also bring back some of her jewelry when you meet her in DC.