I would add a nice eternity band.Yeah it’s definitely Italy thought provoking for fashion / dress jewellery but natural diamond is the standard and remains so. Moissanite has been around for quite some time and we still cling to what is most ‘real’ (diamond) like.
We havent abandoned diamond standards to rock huge mermaid rocks shooting green and blue rainbows.
Going back to the OPs original question I would retain the original diamond and go for a natural diamond three stone for the e- ring upgrade - and, go for a moissanite tennis bracelet or earring studs on the side.
Part of the value of the ring is the brand name. If OP gets the ring transformed, her investment will lose ton of value.