I would probably begin by removing the weedy vine that is growing on my property, and that sometimes means pulling a large portion of it from another area. Perhaps if she saw you were going to take action without her input, she may be more agreeable to conversing with you about it. I don't have any concrete answers, but perhaps this may be a way to open up a dialogue.

Send a certified letter to see if you can get her attention. Other than that, you might talk to an attorney about your options if the tree actually damages the retaining wall.

One thing's for certain,whoever said good fences make good neighbors was wrong. The only thing I could emagine holding her back is lack of funds. You might make it clear you are willing to pay for and/or perform all that's required if she will grant permission.

I've removed as much of the vine as I can reach. Much is growing over the top of my own vines way above the 6' privacy fence. In the note I wrote I asked for permission to come into her back yard and do the work myself. I was extremely polite. Last week DH got a step ladder and reached over the fence as best he could and round-up'd what he could reach. Tonight he's going to concoct a more lethal solution and do it again.

And she still has made no effort to communicate with you??? Incredible !!! I hope this latest effort by your hubbie will result in a dead wild vine. So sorry this is happening to you.