If there was powder on the wheel then that supports the theory she's been running in the wheel with the chew slowly causing the cuts (the powder probably wouldn't have been there if the chew had just sat in the wheel). After hearing that I do definetly think that Alex's guess was right and the daft ham just joined the club of really, really silly rodents lol
Good plan moving it well out of the way, and I'm sure they will heal fast. Most hams do
(Oh and I know what those bridges are like and I really don't think she'd have managed the cuts on that, especially not with how symmetrical it all is, so yeah, I'd try and relax a bit and just keep the daft girls mineral block away from the wheel... Dopey hamster...)
I also really don't think thats mites. Fur loss is a sign as is more scratching and I doubt changes'd be symmetrical. (Plus the legs lack fur and most parasites prefer safer places to hide than the least-furry, most-open places.)