She needs to eat about 20lbs of hay daily. Horses that go many hours without feed often develop ulcers. This is where these small mesh hay nets are good. The horse has to nibble rather than eat large mouthfuls. The hay lasts longer because of this. The nets need to be hung so the horse doesn't paw at it. It will last much longer. Two nets stuffed full should last your horse until the next feeding or close to it. If you can get senior's feed I'd feed that rather than beet pulp. It has beet pulp, extra oils, and is balanced for the old horse as well as the hay.