I think you hit on the key point right here. Employment at Will. If it is in the policy of the organization to provide services and not exclude the homosexual community (and with current social consciousness towards this issue, I find it doubtful they wouldn't have a policy like that) then there is every reason to terminate the employment of an employee who refuses to adhere to it. She really has no legal precedent upon which she can display a "right" to work there. If that's her feelings on the issue, very well, try your luck with another organization who doesn't have that policy, if such an organization exists these days. Try her luck in the community of her church denomination maybe? I wonder if she'd deny counseling services to an individual if they revealed they engaged in other "sinful activities", if so then at least she'd be consistent, but I doubt it.