Let he who is without sin cast the first stone. Besides, what sin did this woman commit? The woman isn't being stoned-- she was asked to repent of the activity that violates her church/school contract. The stoning will come later-- if she doesn't repent. It could be difficult to find someone without sin to cast it, but God-willing, (s)he'll do it. ;-)
The word stoned isn't to be taken literally. It means don't be so critical of others, especially since they are not directly hurting you. She didn't commit any sin, she did nothing untoward to the Church and she didn't perform in the church per se. It's none of the church's business, nor yours, to take action against her since she has broken no laws and is not harming you or the church.
No wonder liberals can accuse, accurately, conservatives as being sanctimonious busy bodies who want nothing more than to censor the private lives of everyone else.