Wow, tough crowd. At no point did you say you were looking at typical diamonds but you're still getting jumped. My interpretation is that you're not interested in mined diamonds and are already aware of the massive ethical issues.

I can't tell you if she actually wants an expensive ring with a big rock, despite what that other comment assures you. That's something you have to determine. My SO wanted something pretty and durable, not expensive. She meant it. She also picked a stone in her favorite color. I think it's flanked by small diamonds for that sparkle but it was only $350 at a department store. I guess at this point I should mention why she did all the shopping and why I don't really know: I proposed with a paper ring and quoted Taylor Swift in doing so. Rather than take a guess and potentially be way off from what she's been looking at on her own, she was able to choose it herself. Some people may be upset that you didn't do all the traditional work, but that's between you and your SO and for you to determine acceptability. A woman with established desires (beyond price) in a ring has likely already done a ton of shopping.

If she tends to be rough with her hands, diamonds are still the most durable stone available. It will take most stones a long time to be visibly scratched, but it happens - especially around sand. That also means if she loses jewelry, the ring may not be around long enough to matter.

I wouldn't recommend silver since it's softer and tarnished a little faster than the other options.

As far as cut, you're really getting into an opinionated area. Some people like the traditional cartoon cut, some like an older oval, some a rectangle, etc. It depends on her style and how loud she wants her jewelry to be.

It's a very variable topic. The only thing I can say, and this applies to many things, is that when you get down to the final 5ish options, no one else will know what you chose between. You'll forget too. They'll probably all be nearly identical if you were to describe them on paper without a picture. There's no such thing as perfect but you always come to simply accept something for being what it is. I went through this with dozens of paint chips when remodeling a house. Once the walls are painted, your guests will never know nor care how long you spent choosing between G305-03 and G306-03.