Michele,

I am about the same height as you and am now riding a bike that is much "bigger" in size than the Trek 5200 47 cm I had. So don't let the different numbers put you off; every brand is different. The slope of the top tube made a big difference for me, and customizing my handlebars. My new bike is a 51; I don't know how it fits, but it does.
I hear you on the size thing. I really think short/small people are discriminated against. My husband has the same problem. He is 5' 7", which is not abnormally short for a man, but he has a lot of issues finding shirts that aren't xxxl or pants with a 31 waist.
I have had great luck with Terry for cycling apparel. Their x small fits me perfectly. For other athletic and casual stuff, try Athleta. They have many petite pants and their x small tops are not too long. I get my Sidi shoes from Performance Bike.com, which most people here hate, but they carry a full range of sizes. As far as regular clothes, I am down to about 3 places I can get things: Banana Republic petites (there is one store in Massachusetts), JCrew catalog (they are phasing out a lot of the petites it seems), and Ann Taylor/The Loft (where clothes are sometimes either too old ladyish or too ****ty for my taste).

Good luck!