I'm glad you are trying to help your girlfriend. She is lucky to have someone who cares. By cutting, there are many risks. She might get an infection, she may cut a vein and could even bleed to death if she cuts too deep!! She might misjudge the severity of the cut and the cut might require stiches.
Also cutting is like a drug- it is very addictive. Soon they cannot stop. Of course there are also emotional affects- suicidal thoguths, clinical depression. If she has bipolar she has to be extra careful to not cut when she is feeling to angry or depressed or she may do soemthing irreversible.
I'm sorry if this post sounds grim and scary but it is reality unfortunately.
Please take her to see adr. Her life is at risk and she deperately needs your help. Though she may be angry at first, leter when she is better she will thank you. Good luck to you and please post again on how she's doing.
Also is she taking any mediaction for her bipolar disorder? This may also help with the cutting issue.