Good question, VB. I've seen it so often that I don't even think twice about it. I heard the word "she" referring to rings, cars, boats, bbq grills, and TVs - "isn't she a beauty?"
Here's what I've observed - they are quasi-luxury items usually purchased with disposable income, and are not physically attached to the ground, the house, a wall, etc. All of the above items mentioned can be picked up and moved. You cannot take it with you if you moved to a new house. If you installed a marble counter top in a kitchen, it's an "it" versus a "she".
My guess is that these things become your "baby". The $ money you put it in to it, and the pleasure it gives you makes you want to care for it like you do a child. It starts to take on human qualities in your mind.
In the old days, females were to be protected as they were considered vulnerable. So maybe attributing the word "she", or a giving an object a name, justifies the protective care we take of these objects. You know, the obsession of polishing of a car 2x a week, rinsing your rings in bottled water, or a personal example, my husband patting our Weber grill after bbq-ing and saying, "she's been a great work-horse."
Just some thoughts on that - or I'm
the crazy one! After all, I've named the rings in one set, Contessa & Marchesa.
<-- there you go, VB, the crazy face, in honor of you.