Recovering from a severe sports injury through hard physical training and rebuilding muscles that atrophied would qualify as overcoming impossible odds. Using a purple ray or other deus ex machina to fix an otherwise irreparable spinal injury is an easy fix. It doesn't resolve the conflicts Barbara has to face, it just removes them.

I should also note that the challenges posed by disabilities can be as much social as they are physical. There's a heavy stigma attached to any impairment, and having fleshed-out sympathetic primary characters like Barbara in Birds of Prey is an important tool to combat societal prejudice and help the disabled receive better treatment in day-to-day life.