If you can find a nanny goat in milk, you can teach your foal to nurse the goat. We used a big wooden wire spool that our goat would stand on that was high enough for the foal to nurse from. It was years ago and I wish I had some pictures because it was just too funny to see!
Goat milk is much better than cow milk, and in some cases, even better than powdered replacement milk.
And as has already been said, be sure to keep stripping the bad side of her bag to relieve the pressure and reduce the infection.