Take a copy of Katie Scarlett's shot record with you at the very least. I always carry my fur kid's health folders with me wherever I travel. I put it in my checked luggage. Strip down your baby in the car on the way to the airport. It will be easier and safer than doing this at security. Dress and travel simply yourself too, as it will all be lots to juggle (i.e.- don't wear boots, wear slip on shoes instead, things like that). You can
quietly re-dress her when you get to your gate. Take an empty, tiny tupperware with a tight fitting lid. After you get through security, hit a water fountain and partly fill your tupperware, or buy a bottle of water. You don't want to give Katie Scarlett too much to eat or drink, just a few sips to keep her comfy. Let her practice being in her carrier, and treat her so that she learns to associate it with good things. By the way, BWI does have an outdoor pet relief area (as do must airports). It's located at the end of Concourse E near the International Terminal, adjacent to the light rail station. That's pretty far away from the domestic concourse (like concourse A = Southwest Air), so if you are flying domestic, and if you have extra time before travel, consider pulling in the cell phone lot to let her potty. If you are going to do that, then ignore above advise and don't undress her in the car until you finish her potty break
Happy Trails!