So it worked absolutely wonder for 1.5 years or so. But last week she figured out that if she pulls it and then rears she can pull through all rope (or at least enough) and get away to the grass (or to follow me - whatever). She is NOT doing it in great fear or anything, but because she KNOWS it works and takes advantage of it (she's not stupid). My biggest concern is this is a rail with the tieing post in middle so if she'll rear too close to that rail in principle she can land front legs OVER the rail. Not good. I tied her to the tree and she was fine, but the tree location is not really good, plus I can't expect tree to be around if I haul her somewhere.
So my question is - what's the best way to stop that? If I tie her to the rail in "normal" way (meaning no pull through allowed) short enough (like 1 - 1.5 feet from the rail so she wouldn't have enough space to rear) would that solve the problem or she may panic being tied so short?