@BeanWriting
The secret couple are picking and choosing what they want from other people and how they want other people to relate to their friends or even partners. They would like to have support with no consequences or obligations.
One wants unconditional support from a female friend and the right to dictate that friend's intimacy with her own husband. The other wants a loving and committed wife without being a loving and committed partner.
What kind of relationship do you want with your husband? If he is your best friend he will care about how bad you are feeling about your female friend turning out not to be the person you thought they were.
BeanWriting has said it.
God I really dislike Sarah. She has kept it secret because that was the condition it needed in order to flourish. Now she's told you and is trying to dictate exactly who you can and can't tell. She wants the support and someone to talk to about it, but couldn't care zip for the position she's putting you in.
She is manipulating you to:
Lie to your husband.
Lie to a long-time female friend who's in your close circle.
Wait with an awful knowledge that at some point this will all come out and you will be judged and disliked and possibly disowned for not having spoken up.
OK well my number 1 rule is, nobody should ever try to come between partners and tell them what they can and can't say to each other.
Why on earth now would you care if your husband 'loses' Sarah as a great work-mate? Ok, care, but that's not the priority.
Sarah is gone. She's not your best friend any more. She's treating you like shit. So don't put her priorities first.
Your husband is the most important person for you. And your relationship with him.
And Emma and her kids - well. You can't save or help them, but you really really don't want the guilt of having known all about it and having been going to girly dinners etc. and lying through your teeth, to protect a woman who couldn't give a fuck about you really.
This is not your battle, not your mess and not your worry or responsibility.
Personally I wouldn't tell Emma, because that feels way to invasive. Again, it isn't your story, or choice to tell her.
But not tell my husband?!! Hell yes. Of course I would tell him straight away. So it's not just me who knows, so we can talk about it and decide together what we should do, so I'm not alone with it, so Sarah is not manipulating me.
If he's so close to Sarah, then he can sort her out. He can talk to her. This is just too horrible for Emma and those kids. OMG no, don't OP make her force you to sit and lie at birthday parties. No way Jose.