If it doesn’t give her the ick and she likes the classic styles, used jewelry is the way to go. It’s already had the “walk out of store” depreciation and I think engravings on most rings are pretty easy to replace.
As a more personal recommendation, when I ahem “outgrew” my own engagement ring and was too lazy/cheap to resize, I got a “temporary” replacement 10? years ago from here. It was supposed to be moissanite in titanium, did an XRF analysis and the band material was some sort of nickel-less maybe steel IIRC. No idea if the moissanite is genuine, but it’s held up way better than any CZ has, and the band has kept better than silver so props to that.