wow-horses only require 2 hours of sleep each day and usually get it in short spurts (cat naps).
are you sure it isnt fatigue? or something like Lyme disease? or just age?
maybe she needs a supplement for energy during teh day and possibly one for calming at night? (as someone with insomnia i can say sometimes it requires medicating at both ends like that).
essential oils may help also-if you want more info, just leave a reply and i can give it to you!