Thanks for response, folks! It gave me some release. :) My vet didn't even mentioned EMP on phone, but I do remember seeing horses with EPM and they didn't walk good.
She's rarely stalled. More often in winter in snow/rain, but always never in summer time. We had REALLY heavy rain yesterday, so I decided it's a good idea, because then they can eat their hay quietly and they really prefer that (otherwise they stand in shelter all the time). Will see how she'll be at night.
EPMhorse, I'm doing my best to keep it from happening (all my grain is in garage and hay is in locked sheds), they both get supplements (and of course, cool water and salt are there 24/7), and I also havn't seen too many raccoons or possums around, but you just never know. I heard it's a terrible disease to pick. :(