Vaseline works well for pasty butt too. once you give her the yogurt and keep her cleaned up for a few days the pasty butt should not be a problem anymore just keep an eye on her. once her digestive system gets back to normal and the pasty butt is gone I would recommend you giving them the yogurt twice a week as a treat as well as beneficial to their digestive health. It definitely won't hurt them.
Hope your chicky gets better soon.
Hope your chicky gets better soon.