When a hay net is full or mostly full or whatever, it’s easier to get hay out of it because there’s less loose net. The hay presses against the holes.
But once a net is emptier it’s harder, because the hay can just move around inside the net itself rather than be easy to get out.
You could put out multiple smaller nets all at once. Because the nets are smaller, she might be able to get more total out of each before being done with the challenge.
Or, put half her hay in your larger net, cinch it tightly above that hay, and put the rest of her hay in, and tie the top. Creating two smaller compartments in your large net. Because it’s two smaller spaces, hay will be less likely to get “lost” in the net.