First thing is to check her boots. Did her problems start with these boots??
My issues started with a pair of boots that were too narrow around the metatarsal area. This pushed the bones together and started the problems with the electrical shocks.
I since switched to a wider boot and that helped alot. I tried on 10 pair, and went with the Merrel Perimeter.
Next is footbeds. You need to find ones with a metatarsal arch support and cushioning under the metatarsal. The support will actually be behind the metatarsal so that the pressure is relieved and the bones are spread out. I went with Spenco Polysorb total support. you will see they have cushioning and the Metatarsal arch support. Many good brands don't have them, especially the front cushion. I am told that Birkenstock Blue footbeds have good metatarsal support.
I would also say to check her day to day shoes as that might be an issue as well. If she wears heals and constricting dress shoes, get something more comfy.
Mine is better, but I still get some discomfort here and there with a heavy pack. I often walk a bit funny to relieve it, like curling my toes under or walking on the outsides of my feet.
Good luck, and see a doctor and maybe get some custom soles made if these tricks don't help, but definitely check the boots first, that's how mine started.