Definitely ask the vet about meds. I use an anxiety medicine (Trazodone) for Jax for long travel because he does tend to get anxious (but he loves every other aspect of travel -- visiting new places, hotels, new people, stores, etc etc) but the act of being in a moving vehicle for long periods of time can cause him stress. The Trazodone really helped ease his anxiety a lot.
You could also work on training beforehand and having to be in a carrier, work up to longer periods of time so she gets used to it.
Check out the site
Dog Jaunt » Traveling with a small dog -- they have a ton of good info regarding rules, airlines, international travel, etc.
I love traveling with my dog. It's such a wonderful experience and such a fun opportunity for a dog to have. So I don't blame you for not wanting to leave her! I don't like to at all either. Unfortunately my boy is bigger so I haven't considered air travel as of yet. I just don't think he'd be very comfortable being shoved under a seat at 18lbs.
I would bring as much food with you as you can but you mayyy want to try to find a backup that works for her prior to actually traveling in case you need to purchase a different brand in a pinch but get her belly used to it.