Bandit is going through exactly the same thing, I'm brushing him daily, and as soon as I brush him, I can pet him and the fur still flies like mad. You can't slow it down, best just to brush daily, even twice a day and encourage lots of hay consumption, as you want as much fiber as possible helping the gut to keep working. Just keep an eye on poops. Bandit has had a couple strung together with hair, but maybe only once a day and the rest are normal. Also make sure she's drinking lots of water, as that will help too. Otherwise there's not much you can do but just try to minimise what she's ingesting by petting her often to remove the fur with your hand and a brush.