FWIW I have ridden with a carpel tunnel brace (available at most pharmacies) and a rollerblading wrist brace. The rollerblading wrist brace is very good at keeping weight off your wrist but is also restrictive on how easy it is to operate shifters and brakes. The carpel tunnel brace is more flexible but still a bit awkward.

Your choice I think would depend on if your GF needs to keep weight off her wrist or just maintain a proper hand wrist angle so things don't get sore.