Hi-
I was diagnosed with Epilepsy at age 14, while I was in HS. It was an EXTREMELY difficult time. Unfortunately, they know VERY little about this disease and what causes the seizures necessarily (unless there is a brain tumor/injury which they can pinpoint or it is caused by some other underlying disease - Cerebral palsy, etc.) In my case, it was rather unexplained, which is what yours daughter's sounds like.
There are MANY drugs out there, all work slightly differently and all have their own set of side effects. In my case we had to try over 8 drugs before one worked for me. It was a difficult time, I was having constant seizures and the only thing they could do was trial and error. You can't just start or stop a drug either, you have to slowly increase the dose until its pretty high to confirm that drug won't work and as you are noticing, the more the drugs, the more the drowsiness and other side effects.
Stay on top of your doctor, make sure you are documenting the side effects and be sure to make it clear that the goal is not simply to stop the seizures, but for quality of life...no seizures but contant drowsiness, constipation, or jittery hands and headaches, is NOT a solution. The doctors will often only ask about seizure control, but the options have to be weighed with the side effects.
It is a SLOW process, but there IS hope. In time, we were able to find a drug that controlled my seizures without terrible side effects. I still had to deal with a small level of drowsiness but it was manageable. The process took about 2 years. I was on those drugs for about 8 years with good control, then when I got married we wanted to have children and were EXTREMELY concerned about birth defects with the medication; and after several options explored we were able to have a very healthy baby on a lowered dose of the medication, and you know what? My epilepsy went away due to the change in my body through pregnancy. I’ve been seizure free for 3 years without ANY medication; including a second pregnancy!
Hang in there, work with the doctors, make sure they know EVERYTHING that is going on and as others have said…empower yourself with knowledge…research the drugs she’s being put on and ask lots and lots of questions.