As usual, I agree with Loosie.
I would also recommend daily washing of the walls especially with sunlight dish soapy water and a stiff brush. Rinse well and dry. You want to keep the "ickies" out of those cracks as much as possible. Do not put more moisture on the hooves, you will make the cracks worse probably. Nothing will fix the cracks like good and regular trimming. She might need to be trimmed at 3 week intervals for a while to get the cracks under control. Don't dismiss those cracks, they do not appear to be just surface cracks. You can see the depth of the chipping in the pics. You've got to keep the dirt out of there as much as possible. I know it's impossible, but everything you do to try will be a help.
You can add biotin and free choice minerals to her diet to help with hoof health as well as overall health.
The only comment about the current trim state is that 4 weeks between trims should not show that much flaring -- either the trim wasn't sufficient or your horse grows hooves superfast. If the latter, then you should quickly be able to get the cracks resolved. :)
As far as gravel, if she could do it before, she can do it again. Once she has a proper trim, introduce the gravel and hard walkways again. They are good for barefoot horses.