The length of the top tube is probably more important than the seat tube. If you can get the saddle low enough for your height, then you don't need to worry about frame size for saddle height reasons. Then you might have too much distance from the saddle to the handlebars. If you have a longer reach stem (more than 90mm), you could get a shorter one which could bring the handlebars closer. If your stem is already pretty short and you find the reach too the handlebars too long, you could try out some smaller bikes and see how they feel.

And yes, if you are looking at a starting point for frame size, I would start at 54 or smaller.