I have an '09 Jamis Aurora Elite (that I really enjoy, btw), and my sister has one, too. The Aurora Elite, since '09, has used the same frame geometry as the Aurora, so it's an apples-to-apples comparison. I'm 5'7" with a 31.5" cycling inseam and the 53cm fits me very well. My sister is about your size, and she rides a 50cm and it fits well.

Our shop is a Jamis dealer, and we sell quite a lot of Auroras. Based on the info you've given, I would say the 50cm is the correct size. We have sold the next size down, the 47cm, and it is a VERY small bike, suitable for someone who is typically more like 5'0" to 5'3." As for the standover height of the 50cm, my guess is that the top tube clearance will be tight and you might even avoid standing flatfooted over it with both feet on the ground, but that it won't be a big deal. There's a good chance you'll be able to comfortably stand over it, keep in mind the standover height on a geometry chart is just one point on the top tube, which in this case is sloping slightly.

Good luck-