Did they check her vision????
Does she, or is she, on a computer or on a tablet all the time or a lot??? Because if so... staring at a computer screen a lot, for kids, can cause headaches. Also because, of the brightness of the lighting that comes from the screen etc. and all the action on screen that kids look at.
If she is always on a computer or iTouch or any tech gadget like that, it causes less blinking of the eyes and it causes eye, strain. And eye dryness. And headaches. Thus, a person should occasionally look away from the computer screen, and move their eyes around looking at different distances etc., so that the eyes are "exercised" and not strained.
Also, per her age.... it could be hormonal headaches. ie: PMS.
I get headaches before and after my period. And Advil does not even make it go away. But at my age, I KNOW it is because of my period and PMS.
Also, she has a LOT of stress, for a young child.
Stress alone, can cause headaches.
And on top of all that, she has school/friends problems, too.
And with you and the younger kids at home... she must have TONS AND TONS of pressures, upon her tiny little shoulders. Stress.
Poor girl.
Does she have, anyone that she can talk to, and chat with, as a girl? Just someone to confide in and talk about anything?
She NEEDS THAT.
She is 15.
And it seems, she cannot even rely on her own parents, to confide in.
Kids need to have, someone they can talk to. About anything.
It is a VERY hard, age. Developmentally.
She needs someone, to talk to about girl stuff. Or anything.
If she has no parent to talk to, nor trust.... then a kid will get "help" from outside influences. And these are typically, negative and potentially harmful.
She is struggling, in her life.
It is OBVIOUS, that she needs, help and even getting a Therapist for her if needed.
Her Dad is very ill.
My Dad was very ill too, before he died.
And I was an adult by then.
And you know... for me as an adult, it was VERY VERY difficult, to deal with. Lots of emotional stress.
So can you imagine, how HARD it must be for her???
She needs, help. Emotional help... and someone she can rely on for her problems. Not being talked at... but someone she can talk, WITH. About anything. Grumpy or happy or sad, stuff.
She needs someone she can "vent" to.
Being all pent up, with no one to confide in or vent to... is very hard on a child. And she is the "oldest" child there. She must feel so pressured in ALL aspects.