What is the location of the headache - the back of the head, the forehead, right side, left side etc...
I have chronic headaches and have been to a million doctors and tried too many meds that did not help. What finally helped was yoga
There could be a million causes for headaches, I would take your daughter to another neurologist for a second opinion. I would also insist that the doctor order an MRI.
Daily use of OTC medications such as tylenol or advil can cause rebound headaches, it is a serious problem and quite common - research rebound headache or headache with OTC med use. See if that fits your situation.
Muscle spasms in the shoulder, neck or back could cause headaches.
Does your daughter wear glasses, maybe she needs to have her eyes checked.
Does she clench her teeth at night - this can cause tension headaches, TMJ (temporomandibular joint dysfunction, or the joints of the jaw) can cause headaches.
a good pillow can help
massage can sometimes help with headaches, especially if related to tension or muscle injury, spasms.
Poor posture definately can cause headaches - physical therapy can help with this but it will take a while and she will need to continue the exercises after PT ends. exercise that strengthen the neck and shoulders are best
constant looking down at a phone texting or using the computer can cause headaches at the back of the head
Keep a headache diary, include date, time, situation when headache occurred ie: hungry, weather, stress, etc... how bad the headache is on 1-10 pain scale, what makes headache worse and better. Also include any visual symptoms that may accompany the headache. You may discover a pattern You can google headache diary and print one out
Of course, headaches can be a sign of something more serious, so if you disagree with the doctors, go to another and another until you feel that you are getting the answers that you deserve.
I would continue to investigate, I agree she is too young to be on all those meds.
PS: my son's headaches got better after he was diagnosed with Celiac disease and we put him on a gluten free diet - just a thought
Let us know how your daughter is doing