Doctors always call symptoms psychosomatic when they can't figure out what something is. It's how they attempt to save face.
http://emedicine.medscape.com/article/1159385-overview
BTW, can it be narcolepsy? Her eyes move rapidly during the unconscious periods, but no other symptom of narcolepsy is apparent.
I do agree with Caryopteris, doctors like to say it's "all in your head". Don't give up, though---something is going on here, you just have to figure out what.
I had similar symptoms--I still do--and I am 16 now. I would faint, not matter what I was doing. The first time it happened, I was sitting on the couch, and it seemed like I just passed out. I didn't know what happened, so I assumed I was just falling asleep. The worst spill I ever had was walking down the steps in 7th grade. All of the sudden, I saw myself going down, like my legs just stopped working or something. I hit my knee so hard on the stone steps that I popped my knee out of place, and I was in physical therapy for 3 months.
My symptoms started when I was in 5th grade, slowed for a while, and now seem to be coming back full force. I had everything your daughter has had done and more. I saw cardiologists, neurologists, and psychologists, all who, sadly, came back with nothing.
One cardiologist told me that I have an electrolyte problem. What he told me to do was increase my electrolyte and salt intake by a little bit. Not a lot, because that's bad, but a little. The easist way to get salt is through pickles or green olives. When I go out, I carry a little zip-lock baggy with me that had some in it, like a diabetic carrying a glucose tablet with them for low blood sugar. Electrolytes are really easy to get now, too, because it's "cool" to drink water that has electrolytes in it. This water tastes like normal bottled water, and you can buy it everywhere. The most common brand is Smart Water.
Now, as far as narcalepsy goes, I would do my research on that if I were you. Many people with narcalepsy don't feel dizzy before they pass out, they just go out like a light. Then, they perk right back up again after a little while, and usually remember what happened before they fell asleep. They'll come right back in to their conversations or whatever it is they're doing without missing a beat. If your daughter has fuzzy memory, or doesn't know what happened, then I would say it's probably not narcolepsy. Of course, it couldn't help to check...
Talk to your doctor again, or find a new one. Either way, you have to sit down and say, "Look, here's what's happening, obviously something's wrong, so what the hell is going on with my daughter?" My mom used to videotape me falling, and would make me tell the camera what had happened before, during, and after the spills so I could have it there for the doctors. Now, I keep a journal for my neurologist and GI so they can see what's going on. You could try either writing down when your daughter falls and what her symptoms were or videotaping. Many times, when a doctor can see it written out in plain English over the course of hours, days, and weeks, they can pinpoint exactly what tests should be done and what coudl be wrong.
Ask for a blood panel, MRI, and NCV/EMG next time. You mgiht need to go to a neurologist to suggest these things. Also, if your PCP won't listen, look up good pediactric neurologists in your area. If you have to, look up adult neurologists. Your daughter could have the early stages of some illness that a pediatrician won't pick up on.
It's a really long road to go down and its a pain in the ***. After 6 years, I still don't have a clue what the root cause of this problem is, and I have more surfacing. Of course, I don't want to see that happen with your daughter, so I would recommend getting her in to doctors at all costs, even if that means going out of state.
Speaking of out of state, try Children's Hospital of Wisconsin in Milwaukee. That's where I go, and the people there are genious. The waiting list is long, but worth it.
I really hope this helps and that your daughter gets better soon. Let me know how this goes!
~ Em