Thanks everyone! I'll let her know that there are others who have had theirs do it after surgery for a while too and to just watch her little guy and the leg (which I'm sure she is doing). She's actually pretty obsessed over it.
Her little guy is super fast and can fly and jump like crazy and does use his leg (all of them for that matter) perfectly fine more than 95% of the time, so all does seem really good.
Thanks again. It's good to hear other people's similar experiences!