Pregnant horse won't stop eating her bedding.?

How close is she to foaling? You could consider switching to shavings until she's close. Shavings shouldn't be used because it gets caught in the foal's nose and can suffocate it. If you're really desperate, as long as her pasture is clean, dry, and grassy, you could let her foal there. I prefer stall though, since it's easier to monitor and keep clean.