Travis,
I feel like what you have read about letting her alone is probably the best advice to take heed to. In my past experience, I have put the cast on a couple fawns with a low to mid leg break before & it hasn't worked out, but I know folks that is has worked out for. Many times they will break the other leg trying to get up. On a high break near the joint, I have always been told that putting the pins in them under a $600+ surgery is about the only way to have a chance & then infection around where the pin protrudes is hard to keep down & generally ends up the demise. I darted a yearling buck about 2 years ago that I hit about 3-4 inches above the knee and broke his leg. I left him alone. In 2 weeks he was putting light weight on it. In 4 weeks he was walking on it. In 2 months I couldn't remember nor identify by sight which one it was. I would take the chance and let your doe be.