I am on the opposite end of the size spectrum (BIG) so know about bikes not being there. Denise is right - call ahead.

It sounds, though, that since you have been riding a mountain bike, you may not have a good idea of what frame size for a road bike exactly fits you. You might consider getting a fitting (even for a fee) from the LBS if they can do that so you know what the likely options are. Among other things, you might like the smaller brake heads, narrower handlebars, etc. of a female specific design - Trek has one, for example, but most folks don't have the full range in store. Some of my less BIG friends love them, others hate them. Depends on their body proportion, hand size, etc.

When I go shopping for bikes with a friend just starting (has been happening a lot since a bunch are giving up running and moving to riding), we start with a LBS where, even if you don't purchase, they give a great fitting advice (small fee) and service/customization after the bike needs tweaking but buy the bike on line or from a larger store. Most folks don't just fit a bike exactly the way it comes out of the factory, so it is good to know someone who can help tweak this and that.

The other good thing about buying from the local is that, if something doesn't fit but you don't figure it out until it hurts a couple months later, you can get them to switch it out for you, often with no charge. Of course, the switch out concerns may not apply to you, but... keep them in mind.

Good luck!