While it is Helen's right to have her opinion (Religious or not) she only drives the bus, SHE DOESN'T OWN IT!
It's not within her job description or right to determine if someone rides her bus if they adhere to common decency and sensibility. So long as they are not flashers, carrying weapons, abusive and the like it's none of her business what someone wears or does.
Had I been that person I would have taken her name and promptly called her company to report her as well as call my lawyer and sue the company and her.