Probably not.Do you think if it was a sprain, it would take this long to heal though?
It's really hard to say exactly what is wrong.... xray might tell the tale.
It might not even be her legs but a spine injury that never healed right,
might have happened while you were not around to observe it.
Heat stroke is a possibility, can screw up their brains...maybe the part the controls mobility.I'm thinking maybe because of the summer heat.
Sorry, just thinking 'out loud'....not sure there's an absolute answer and cure.
As long as a bird can eat/drink/poop/move around enough to do those things,
I just let them carry on....but I'm not one to go to extremes in 'treating' a bird, other than occasional vitamin and/or electrolyte boost.