I vote, if possible, you take her to see a pro. therapist (depending on where you live, there are often free therapists provided by the state). You need to rule out things like abuse/rape, as well as phobias. In high school I knew several girls who acted out in very strange ways after they were molested, raped, or otherwise abused- not saying your DD has been, but you should go ahead and be sure.
How old was she when you stopped going to the bathroom with her every time? Maybe she just stopped wiping and flushing when she wasn't watched anymore, and now it is just habit- I used to teach a 19yr old girl who did this, and that was her situation. Her parents stopped going with her when she was six, and she just lied to them about wiping, flushing and handwashing.
Also, I taught a 6yr old boy who would not wipe at all. His mom was a germ-a-phobe and was constantly talking about how germs give you diseases and they live in poop. She didn't do anything wrong, she was just trying to teach her child! Unfortunately, he developed a severe aversion to wiping because he was afraid a little poop might touch his hand, and he would die from this... it was very sad.
All kids do things we don't understand- she's probably fine! I just thought I would offer up some possible causes