Hi....I'm a chicken mama! What are your roosts made from. Is it possible she got a sliver in her foot from a rough roost? My other thought was bumblefoot, too. How far does she have to fly down from her roost? Could she have sprained it when she landed?
Are you a member of Back Yard Chickens forum? You can get lots of help on that forum:
http://www.backyardchickens.com/forum/index.php
I hope Bindi is feeling better, soon.