Most horses can't just come out of metal shoes and go completely bare immediately. They adapt to what they live on/work on most. So if she's on sandy soil most, that's as tough as her feet will get.
However, just because horses do best without metal shoes, doesn't mean they dont' need protection (esp coming out of shoes). If you wore work boots all your life, you would suffer quite a bit before you were comfrotable on rocks without them, but if you switched to thin, soft shoes first, you would be able to go bare quicker, yes?
Also, you can't expect your horse to be tougher than he/she lives. Sooo, while I do think metal shoes are bad for horses, boots offer protection for our pampered domestic horses, but allow them to have normal, natural hoof function the rest of the day. After all, if you want to argue that a horse carrying a rider isn't "natural" then there shouldn't be any objection to the idea of needing some extra protection when performing outside of the "natural" part of their existance. Most domestics don't move around enough to develop the prime hoof we all covet. We don't have time to condition them on rocky mountains, some of us live on loose, sandy soils and have real jobs that mean that mean our horses are in stalls part/all of the time. So get some boots for when you want to go beyond the usual places. Just know that boots, whatever brand, allow for better hoof mechanism than any metal shoe can, period. In time, your horse may not need any extra protection, but even if she does, she'll be healthier for being bare as much as possible.