You really sound like it's privacy you're after even if they are playing nice now. I hear ya' there! We have been through hell with our neighbors...I know what I am talking about on this one, UNFORTUNATELY. Fences aren't cheap and neither are bushes and trees, but I think that if you start planting some privacy bushes and maybe changing the placement of things in your yard if at all possible to angle a little more away from them if at all possible, she might get the hint. Just do whatever you can to establish boundaries but not anger them. Neighbors can be wonderful and they can ruin your life...you're still at the point where you can control how this turns out, for the most part anyway. So far, so good, and it is perfectly fine for you to ask them to come to you first before going right back to see the birds. BUSHES, BUSHES and more bushes! If all else fails, you will have to put up a fence...good luck!