The ridges are - stress rings, growth rings, grass rings. Typically brought on by systemic stress within the horse. Changes in environment, diet, a fever, illness, etc.
...And mechanical balance. For eg. the rings being 'wavy' rather than level, such as the inside of the right fore where it's more flared & excess ground pressure is putting more stress on the wall.
While your farriers have seen & felt her feet & presumably seen her use them in person & we haven't even seen pics of the base of her feet, so we can't know better, from those pics I'd say it's likely that horse does indeed need hoof protection, for now at least & on rough ground at least. She may well have great feet eventually that will do well bare, but I think it's likely getting them healthy will have to happen first. Especially given the weak, disconnected state of the walls, I wouldn't want to use shoes for this for now at least, but hoof boots are a valid option.
You mentioned her feet looking uneven? Haven't got the pics on this page to check while I write, but is the right fore more upright & flared toe than the left? It's common for horses to be uneven & generally not something to be 'fixed', at least with trimming alone. The feet need to be managed to keep them in good balance, but that doesn't necessarily mean making matching pairs.
Yes, it likely will take the time for the rubbish growth to grow out before she gets some real strength to them and IME frequent enough trimming to maintain form & function, rather than waiting for them to overgrow & distort more before trimming is important. That may or may not mean more frequent trimming to what she's had & horses feet grow at different rates at different times, depending on diet, environment, exercise, etc. so just because, say 5-weekly is a good schedule now, doesn't mean it always will be.
Studies have been done on supplementing Biotin and have shown that it does help. Unfortunately, so far as I'm aware there are few good scientific studies on other specific nutrients, but there is a lot of anecdotal evidence. It is but one of many nutrients that are necessary for hoof(& the rest of the body) health, that may or may not be deficient in the diet. Minerals & other nutrients, water and an energy source by way of food are the necessary building blocks of life, so I don't think supplementing missing/imbalanced 'ingredients' is superfluous at all. IMO supplementing with minerals *appropriate for that horse & diet* is an important part of healthy hooves.