Was there an actual Sally that Sally's Beauty Supply is named for?

Yes, Her name was Sally Josephine Deluca. Sally was the daughter of the man who owned the original Sally Beauty Supply in New Orleans, LA. She was the original founder of a small store in post war America. The store became part of Alberto Culver and is now an independent company.

The store was called Sally's Beauty and soon developed into a bigger brand which you now know today as Sally's Beauty Supply. Her success has made the store internationally reknown.