Depression is an occasional side effect of epilepsy medicines.
She may have to change her combinations to combat this. Usually, doctors start with one and add others once monotherapy on the whole range of medicines has been exhausted. Often, multiple epilepsy medicines are unneccessary and only lead to additional side effects. Perhaps she should see another neurologist for another opinion on her medicines. Try to find one who specializes in epilepsy, preferably at a major epilepsy treatment center.