It depends. Was this counselor working for a church or a public firm? That's what really matters in this case. Once you work for someone else, you agree to follow their rules as a contingent for continued employment. You can't suddenly decide you don't want to do your job because it interferes with your religious beliefs. If there was a pre-existing agreement that said counselor wouldn't see gay couples, they might have a case. If not, and they work for a private employer or for the government, they're completely out of luck.
Religion does not *EVER* grant one permission to discriminate in public life.