I am leaning towards right now just getting a fence to separate our houses.
Make sure you know where the legal property line is first, or you will make things worse instead of better. If your property has not been surveyed, or if it has but you cannot find the corner pins, then at least get an estimate from a licensed surveyor. Ask what they would charge to survey your property, locate or install corner pins (depending on whether there are already pins from an earlier survey), and get their survey recorded.
BTW, the place to look to see if your property has already been surveyed is the official property records at the county recorder's office (or whatever it's called in your county), the same place where you'll find your deed and your mortgage if you have one. If you find a survey there, you can try searching for the corner markers using a metal detector. Corner pins are usually lengths of rebar driven into the ground, with colored plastic caps on top with information identifying the surveyor.
Before you spend any money, though, have you asked your neighbor what makes her think the 2-foot wide strip of land in question is on her side of the property line? Did she get a survey done, or find any corner pins?