I am in the same boat for my GF. She is 5'1". I have been looking for quite awhile now. What I have found in the smaller sizes are:
Bianchi San Jose 44cm
Fuji Track 43cm
Surly Crosscheck 42cm also comes in 46cm
EAI Brass knuckle
For doing a conversion, I have been looking for a decent frame in a smaller size and they are hard to come by. They didn't make too many frames that small in the 70s. Most of the ones that I do find that would be a good fit are too rusty or not even worth the time.