Lady appears to be a freelance design, with no real known locomotive prototype. But it's possible that her design might be based on the Great Western Railway experimental locomotive numbered 101. The GWR 101 was withdrawn and scrapped in 1911, as it was the only single engine built just for experiment tests.
Lady is painted red-purple with gold head lamps on her front footplate, tail lamp, gold buffers, smokebox, funnel top, dome, whistle, side rods, lining and her name on each side in gold. She is also painted a very dark purple on her cab roof, lower funnel section and her footplate.
In equine form, Lady is a unicorn mare with a red-purple coat, golden hair and hooves. With purple eyes. Her cutie mark is a swirl of gold dust.