She has a name! Rosalyn had always loved helping people fix their things, but it wasn’t until her own accident that she realised she could fix broken ponies as well as broken carts.  
When she received a fairly crude stick of a replacement hindleg from Ponyville hospital, she set out to make her own design, the results of which you can see above. As she took her first steps on her new limb, she decided she would devote her time to helping other ponies like her, and become a prosthetist.