My son started the ketogenic diet about 10 months ago and his seizures were cut in 1/2 in a few days. He was still on a little medicine but we took him off after about a month or so. He has done better off of the medicine than on. We tried 6 or 7 with no success. If you don't have success at first just give it a little time and if you are not already consulting with John Hopkins hospital I would recommend that you call them if you still don't have success.
Just a couple of tips:
1. Monitor her weight and adjust the diet accordingly. We have found that when we don't keep up with my son's weight precisely and adjust the diet he suffers.
2. Watch out for artificial flavorings, colorings, and sweetners. You may already know about this but Mono-Sodium-Glutamat (Natrium Glutamat) and aspertam and some artificial colorings will cause seizures. I can get you more info on this if you want and I'm sure other people on this site know as well.
3. Make sure she doesn't steal food or drinks. We have other kids in the house and it is really hard to sippy cups of juice and milk away from him and sometimes if he has a bad day it's because of stealing just a little food here or a drink there.
We haven't had total success. He still has seizures and that is just part of the battle but the ketogenic diet has helped and it allowed us to get him off of the medicine. Just give it a little time.