I'm a hair bigger than you 5' even 5' 1/4" if you believe the last person who took my height, but I think she didn't squish down my hair..... with about the same inseam as you. No way I could ride a 50! I'm on a 44cm on my 700c wheel bike and a 47 on my 650c.

Regardless of stand-over, unless you have very long arms, I'd wager that you are waaaaaaaaay stretched out on that 50. You should be able to have a very comfortable bend in your elbows when reaching the handlebars. If you are reaching straight out the bike is too big.

Oh.... I can see the hub over the handlebars on all of my bikes....