Okay its quite simple. First take your friend and place her in the first spot with 4 paths leading out( the area when you first walk in). Then just run up to Furfrou and it will run to the back of the garden. Then you go back and grab your friend and tell her to wait in one of those two spot above the other area(doesnt matter which one). Whichever you told her to wait at you go the opposite way and Furfrou will be caught.