Most feed scoops are 3qt, at least in all the feed stores around here. I have a 1 qt feed scoop and it is SMALL. I use it for adding a little oats to a couple of horses who need more energy.
Take a scoop of your feed home and weigh it. If you don't have a kitchen or postal scale, take the feed (in a baggie) to the grocery store and weigh it on a produce scale. If your scoop holds 3 lbs of feed, she would need 2-3 scoops a day. You should not feed more than 5 lbs of feed (total) per-feeding.
If they clean up their hay in 2 hours, then that's not enough hay. You want a thin horse on 3-4% of their body weight in hay every day. That's about 30-40 lbs of hay for a 1,000 lb horse. If your bales are moderately heavy grass bales (50-60 lbs), then you need 1/2 to 2/3rds of a bale per-horse every day.