increasing insomnia (11 yr. old girl)

Sorry, a lot of this is copied from the bipolar check-in thread. I'm beyond exhausted.

My daughter (11 years old) had insomnia last night and kept getting more and more anxious as the night wore on, waking me and crying. She did not go to sleep until 5 or 5:30 AM. After she kept waking me, I could not go back to sleep after 2 AM. Woke her around 10:30 AM, had a sort of brunch and took her to school around noon (though she's still counted absent). But at least she won't miss her 2nd teacher's instruction after lunch and can get her homework from the morning class she missed. I only got her to sleep giving her children's Benadryl, but this keeps happening (though usually not this extreme, and this is the 1st time I resorted to children's Benadryl).

I just don't know what to do. It doesn't help that I've read circadian rhythms change for teenagers, and though she is only 11 (5th grade), she is advanced physically and already the size of a small adult, 5'1" tall and just over 100 lb. And she's always been ahead mentally in all her subjects even if she is behind with some fine motor skills (brushing out hair tangles, climbing down stairs, tying a bow), but it seems to be getting better with things as time goes by. I am pretty sure she has sensory processing disorder. We just can't afford to get it diagnosed & get the occupational therapy she needs as most of the things she has issues with do not affect her school day, so the school does not pay for any treatment.