Look at the EurotekPro with the 11"dd....that should put you right at 300...get her a light fast longhandled scoop with a 5" bucket.
Reason: You need a fast, light, comfortable machine to work a lot of dry sand...everything has to be light, fast and comfortable to cover ground. Even that small scoop is important to balance out a person working dry sand...too big a scoop and you wear yourself out...If you get her the right gear upfront, she will be less likely to call it quits...With a package like this, she should be able to outhunt most in short order.
Working the dry is a slash and grab sport, swinging wide and fast, reading the beach, hitting the out of the way higher sand,. For the serious dry sanders, it takes a lot of endurance and is a skillset unto its self.
Pretty much any old detector WOULD work, its just that what would really work the best and the most comfortable for this kind of hunting...even how you swing is important, a person can sort of crouch and move with a wide legged pace with your body swaying from side to side...it looks goofy, but it will extend your swing to about a 10' arc with no tiresome wear on your arm, your arm is not swinging, your whole body is and your arm is just guiding the coil with momentum doing the work...a general whole body workout! Its all about the prime realestate covered the quickest that wins in dry sanding.

Doing a little figuring, in July alone I covered 100 miles on the dry, barefoot. Nearly every morning very early, down and back on some prime beach, cutting a wide swath and smokejumping the towel line. .tough duty..good Luck!

Mud