Strictly speaking Epilepsy is not one disease. It is a term used do describe a condition where a person has repeated seizures. So, your daughter could be said to already have epilepsy. This is not to say that she will always have it.
My daughter started having myoclonic seizures at about 14 months. The way it was put to me (in 1987) was that I had better be aggressive about treating them because the brain likes to do what it is used to doing, so if seizures continue long enough over time, the brain gets used to having them. We tried lots of medicines in quick succession and tried the ketogenic diet but did not get control of them. She was having hundreds or thousands a day. The only thing that stopped them was daily injections of ACTH. Some children, when they are weaned off of ACTH, do not resume having seizures and some do. Myoclonic siezures are sometimes difficult to control, more difficult than other types of seizures.
I am not trying to scare you but it doesn't help to hide your head in the sand either.
One of the things that I didn't appreciate was the overly optimistic advice not to worry because seizures can be controlled with medication. The fact is that about 25% of people with seizures do not gain complete control with medication. If you are not in a big city with an Epilepsy center, I would get to one. We went to the Cleveland Clinic where they have some of the top pediatric neurologists in the world. There are other well known places like Johns Hopkins etc.
My daughter is now 22 years old and still has myoclonic seizures but also has grand mal seizures. What I was told is that myoclonic seizures are the way an immature brain seizes and often as the person ages they will transition to having grand mal seizures. These at least tend to be less frequent and are easier to control.
The condition you mention with teenagers, juvenile myoclonic epilepsy, is a specific condition that causes myoclonic seizures. But there are lots of young children with myoclonic seizures. What you want them to do is figure out, if they can, what is causing them. There are lots of conditions that include seizures as one of the symptoms and you want a complete work-up, which will probably involve a few days in the hospital, to rule out some things, like metabolic problems, as a cause. Everyone has what they call a seizure threshold. My neighbor cut his finger off with a power tool and had a seizure. This had a specific cause and he will probably never have another. If you can find a reason and eliminate it, then you can bring things under control. Sometimes they don't find the reason or see anything on MRIs or CT scans or metabolic or genetic tests and then you are said to have idiopathic epilepsy. In my daughter's case, she was born 10 weeks early, weighed 2lbs. 6oz. and was on a respirator for several weeks. She was oxygen deprived and has very slight damage to the outer cortex. There is not one spot on her brain that generates seizures so she is not a candidate for the type of surgery that would remove the spot.
At the risk of giving you too much information, you should see your doctor, make sure that they do a thorough investigation and that their credentials are top-notch. Don't mess around with a pediatrician who thinks he can handle it or a neurologist who does not specialize in pediatric seizures.
I will pray for you and your daughter