I am also a 'cutter'. I started as a teenager and it is VERY difficult to break. Cutters feel an emotional release when cutting and you almost get a 'high' from the endorphins that are released.
It definitely sounds like bipolar because in my experience everyone thought I was just ADD and depressed (mania often appears to be add), but FINALLY after YEARS of misdiagnose, I am doing much better.
In my experience, Geodon has worked the best for me. I am suprised that the doc's started her on Lithium first in this day and age. I take Lamictal and Geodon and it has worked for me. SOmetimes it takes many tried before they find out what works.
Cutting is often associated with sexual abuse in young women (it is in my case as well), so are you aware of any abuse that may have occured?
Therapy is a MUST for any cutter, so that's good that she is going.
Cutting is very much so an acting out behavior, so she is trying to tell people how much she hurts. Does she have other ways to express herself that are healthy? For me, it's music (piano, violin, singing, etc)
Some kids do well with art, writing,etc. Is thee a healthy hobby in her life that you can encourage? That always helped me.
Being involved in church also has been a tremendous help. I credit making it through my teenage years without knocking myself off to God and my youth ministers.
I will pray for you and your daughter because I believe that God can help and that you find doctors that are the very best for your daughter. I know cutting is very disturbing (and enbarrassing when youa re older), so I hope that she gets the help she needs to stop now. Hang in there and know that there is ALWAYS hope, no matter how bad it gets.