My question involves real estate located in the State of: IL

I bought my house 9 years ago. The previous owners of my house supposedly built a retaining wall on my neighbor's property (supposedly received my neighbor's permission to build). My neighbor told me this last year, but now is denying it. They are saying the entire wall in on their property. To know for sure we will need to have a survey done. The last 10 to 15 feet of the wall curves in about 2 feet further in on their property. It was like this when I moved into the house. (I don't have pictures of this and don't know if any exist.) I don't have any plans to fight them on this and they are not asking me to remove the entire wall, but the last 10 to 15 feet. They want me to make it straight as they thought it was originally. They are accusing my brother & cousin (who was doing my yard work) of moving this wall. They never touched this wall. My other cousin was also present (not doing any work) which can testify that they did not touch this wall, but only the weeds surrounding it. During the past week, my neighbor knocked over many of the bricks that was part of this retaining wall. Many of these rocks are now on my property. I would like to resolve this without us having to go to court. I am afraid if I touch this wall, then she will come after me for her property washing away. The dirt has to go somewhere. If they want to remove this wall, I am OK with it. If the dirt falls on my property, then I am OK with some free dirt. I am not that difficult of a neighbor and very easy going. If they say this is their property in which it is probably so, then please take it and take what is on it. My boss at work suggested that I call my title company and the city for them to make a ruling (this is apparently free). Any legal advice on how I should handle this situation would be very helpful.