You are a little smaller than me -- I'm 5'2" and have a 28.5" cycling inseam and long femurs. I was perfectly fitted on my 17.5" Terry Isis back in the day and have also had a 46 cm bike that fit me. I can also ride a 47cm Trek (possibly needing a slightly shorter stem on that one).

I am sure there may be some models/brands in which a 48 cm would work for me that I have not had the opportunity to try, but I can't imagine any bike that would fit me in a 50-51cm.

Just wanted to chime in for comparison purposes. I think it's actually quite possible that a 44 cm would fit you, but no way to know until you try one.

Good luck!