I've had a SEVERELY broken leg for 4 years now and have been on and off Vicodin too many times to remember. If you are really in pain it can make life livable and keep you productive but when you take them just so you "feel better" then it becomes a problem. There is only one good way to get off them and that is a gradual reduction in dosage. You have to be SUPER strong to go cold turkey!
How many does she take a day? More than 10?
She has two things working against her and that is her body and her mind. They have to slow down at the same time. Is she still in pain? Is it real pain or does she just think it's pain? If she knows in her heart that the pain is gone, or at least low enough that she doesn't need the pills, then she can reduce her dosage for a few days and see how she feels. If her body wants it but her mind knows she doesn't need it, then the cravings will subside quickly and she could be done in a short period of time.
When I was just out of the hospital I was on a Fentenyl patch which is a very, very strong pain killer. I changed it every 3 days and never considered it an issue. After about two months of healing I was moving around and took a dip in the jacuzzi. The patch fell off. Around 2am a woke up experiencing the worst kind of feeling I ever had and was totally oblivious as to why (no babies crawling on the ceiling, but close). I was literally freaking out. My wife noticed the patch missing and even though it would take some time for the meds to get back in my system, just me knowing that I was getting my "fix" calmed me down. Thats when I knew I had a problem. I started reducing my dosage and was finished with it in a month.
It's rough, but it sounds like she wants off so it will happen. Like Laser said, Vicodin's are easier than most to kick.