Like I said on another thread, you need to actually weigh the feed to see how much she is getting. Take the empty bucket, weigh it and then put in the feed and weigh it, then subtract the empty bucket weight and you know exactly how much you are feeding. Then check the bag and see the suggested amounts in pounds that your horse should be eating and figure out if you need to feed more or less each feeding.
Back to the same story with Bones, he was horribly underweight from starvation. When I started feeding him Senior feed, I read the directions and fed what I thought was the right amount. Then I realized I was feeding for a healthy weight horse. I realized I needed to give more. Then I weighed what I had thought was enough(was scooping feed with a scoop) and realized it was half of what he was supposed to be getting. He was to be getting 14 lbs of Senior feed a day, so I weighed a bucket for 7 pounds of feed, marked where the 7 lbs came to in the bucket with a marker and gave him that amount twice a day. Went through bags of feed really fast, but he sure gained weight quickly. Oh yea, he was 21 at the time, he is now 23 and fat and sassy. He also got free choice hay 24/7..... I kept him seperate from the other horse for the first mnoths until he gained enough weight not to lose any by stressing him when putting him in a new place.
I stated it once and will state it everytime. Weigh Weigh Weigh the feed, both grains and hay if she is not getting free choice. It will make a difference if the horse is healthy in other aspects.