When you ask your doctor about Sudafed for little ones, also ask about trying it out before the flight. Most kids will get sleepy with it, but it is possible to have the opposite effect and become hyper from it. You don't want to give your first dose just before getting on a plane for a 3 hour trip and find out it makes your child hyper-alert and irritable.
A sippy cup, snacks or a bottle are more controllable options.
I don't know how they work for smaller kids, but a lot of people have posted about EarPlanes. They are earplugs that are designed to help with the pressure on airplanes. If you do a search, you should find some postings about them.
While you are at the dollar store picking up some new toys and books, also look for some various size gift bags. 13 month olds usually enjoy putting things in and out of bags. If you have various size bags and some tissue paper to hide things in the bags, that might keep her occupied longer than just having the new toys would. If you have bigger and smaller bags, she can do things like put one bag into another. The nice thing about gift bags is that they can be folded up to a flat small size when done.