I would feed her just a ration balancer, like Purina's Born or Win or Mare & Maintenence, or Triple Crown's 12% or 30% supplement. You only have to feed 1lb a day for total nutrition with a ration balancer. They are simple too, and shouldn't make a horse hot/hyper.
Another thing to consider is that horses deficient in Magnesium and/or B vitamins can cause an otherwise calm horse to act hyper. If the ration balancer doesn't cool her down, you might add a supplement to her feed for both. http://www.horsetech.com
will custom blend you one, so you only have one bucket. They are very nice to work with and their supplements are top of the line. Just give them a call and ask them about a custom blend.
The last thing to consider is that your mare needs more turnout. As long as she has a good winter coat and there is shelter form wind and rain/show in the pasture, then she doesn't have to stay in all night. Just have her stay in to eat her food, and then turn her back out, only keeping her in when the weather is especially bad.
Oops, one more thing to consider! If she's gained or lost any weight since the summer, even just a little, her saddle could be not fitting her properly and causing her discomfort.