Welcome!

I am a bigger gal myself, and at 5'4 I am very comfortable on my 52cm frame. I'm sure you will find a great fit - IMO it all has to do with getting knowledgeable and patient service. I second all the advice given on trying a variety of bike shops until you find one where the staff will go out of their way to make sure you find what you need! When I purchased my cyclocross bike the guys at my LBS took the time to pull out every bike they had that might fit, they measured, adjusted, tweaked, and even got other staff opinions to make sure I had the best fit possible. They even offered to order in anything I was interested in trying if I didn't find a good fit with what they had in stock.

Another benefit to finding an LBS with great service is the support and kindness that comes with getting to know them well. When I expressed concern about my size when purchasing my bike, they were able to (gently) ask relevant questions, give me honest, helpful answers, and otherwise reassure me that my bike wouldn't fail me! Now when I stop in, they know me by name, are genuinely interested in my progress with cycling and how well my bike is working, and often have news about stock that they specially ordered thinking about me and some of the challenges I have in finding the right gear and clothing.

I wish you all the best in your search for the right fit!