At what point did you suspect
That Lee wasn't fully human?
For me the moment I started to suspect that she might be enhanced was when both she and Morgan fell out of the second story window, and both just got up and pretty much shook it off like nothing.
Then when she was impaled by the tree branch, I thought that's if for her, but when she was standing on the pier behind Morgan at that point I was pretty certain that my hunch was right.