Mojssanite (sp?) and zirconium stones have those properties as well, and cost much less. Some other gem stones are very hard to distinguish from diamonds withou

Mojssanite (sp?) and zirconium stones have those properties as well, and cost much less. Some other gem stones are very hard to distinguish from diamonds without specific tools. Does your sister have a preference for diamonds over finely cut zirconium (or even glass)? It’s likely not as simple as that, even if you and her try to rationalize it that way.