I really don't want to be rude but I need to ask - Are you a stout 4'8" or a petite 4'8"? If you are the former you may want to go with the 12 ga if you can handle it. Depending on your budget, I would definitely go with the Browning or Beretta O/u if that's what you like and if it FITS you. If you are petite, go with the 20 ga - again same guns.
If its an autoloader your looking at, Benelli or Remington would be my choices. As for barrel length, for a woman your size, I would go with 26" and screw in chokes.
Don't worry about the autoloaders and being left handed. I'm a lefty and use a Remington 11-87 a good bit. In my younger years I never wore shooting glasses and if the wind was in my face I would occasionally get hot powder in my eyes. Not very pleasant. But now that I'm older and wiser, I wear shooting glasses and don't have this problem. (If your shooting Clays, the rose colored glasses make those orange birds stick out like neon signs.)
ps: glad to see women getting involved more in the shooting sports. Good luck to you