I'll start by saying we have no problem from her carefully cutting any bits that are encroaching on her side (the ivy is the only thing holding the fence together...), but she's taken 2ft off the top! The ivy had basically grown into a thick hedge around and over the top of the fence and she's just hacked it right down. It was blocking our view of their garden and now when we sit in our living room we have a direct view onto their decking, and obviously they now have a direct view into our living room.
I get that ivy is totally annoying and destructive, but it's not her fence to worry about, we own it. We are planning on replacing the fence eventually but we don't currently have a few thousand pounds spare to do it. I said to DH we should put some trellis on the top of the fence but ivy is so slow growing that we'd probably have a new fence before it grew back up!
FFS.