M.S.
After 9 weeks, her muscle tone has diminished significantly, so she has to build back up. Activity and physical use of muscles, they will gradually strengthen. Building back is always slower than the decline. Remember, her balance has been off due to size and weight of cast and boot, so she has favored that side a long time and muscles on the other side have been compromised as well. I would not think anything abnormal at this time. Her security in using muscles will improve soon as long as she isn't having pain. Right now, it should be weakness more than pain. With lack of use, the muscles and tendons will atrophy and weaken. Remember this is a case of "if you don't use it, you lose it". Just like if you haven't been exercised and start a program, you have to work up, you can't run a marathon the first time you try to run. It takes practice. She has to do the same.
Maybe a physical therapy evaluation would be of benefit for some strengthening exercise to speed up the process. She did not wear the cast too long. Bones take longer to regrow than soft tissues.