Going to order a cam walker, have a broken foot, 5 met bones, the size for small is 6 to 8 and I wear 7 1/2. Med is size 8 to 12. Which should I pick?

Consider ordering . Both and returning the one you don't want.
Cam Walker boot. Fracture boots usually only come in about 4 different sizes so it'll never be the exact size of her foot. I tend to give boots that are slightly larger as this will help prevent you from stubbing your toe. There is variability between manufacturers so the best way is to try it out before you leave with it.
You pick. Ya, tough one: smaller runs the risk of toes hanging off the edge (not good for metatarsal fractures); larger runs the risk of too clunky and big. I would error on the side of larger. Go medium.
NWB cast is better. Small-size camwalker boot. But, i would recommend strict nonweightbearing (nwb). Better yet, a nwb below-the-knee cast will provide more stability and adequate immobilization.