If she likes him back the same way, she'll say "Hooray! Guess what, I feel the same way about you! Let's date!"

If she doesn't like him back the same way, she'll think "Ew, awkward. I don't want to hurt his feelings and I'd still like to be friends with him, but I don't want to lead him on either." And she'll likely say something like she's not interested in dating right now, or she likes your friendship just the way it is.

If she didn't say much of anything, it's safe to assume she doesn't feel the same way but she hasn't figured out a way to let you down gently.

If this is a deal-breaker for you, the only possible way to change her mind is to tell her exactly that - and then be prepared to follow through. It's probably not too soon for you to lawyer up and start talking about divorce and child custody, if she is determined to go through with this terrible plan.

If you married with the assumption of monogamy, you absolutely have a right to insist that she remains monogamous if she wants to stay married to you. She voluntarily chose to limit her own sexuality and restrict access to her body, when she took her marriage vows. Don't let her try to accuse you of anything more than reminding her she's married.

OP, I think it's fair to point out to Jay that Logan is being his old manipulative self again, and quite possibly trying to break you up by inviting Jay to the wedding without you. Tell Jay that he has to make up his own mind about this, but if the roles were reversed, there's no way you would agree to be Rose's maid of honor if your BF was excluded from attending the wedding.

If he doesn't already know, you should also tell Jay about how Logan used to flirt with you before you and Jay met, how he would pry into your personal life (based on snooping Rose's phone) in ways that made you uncomfortable, and how in your opinion he's never been a very good BF to Rose. Remind him about all the times that Logan has messed with him personally, and about how peaceful the last six months have been without having him in your lives.

Finally, tell him what (if anything) will break your relationship if he decides to be Logan's best man, and Logan manipulates him into a compromising situation with one of the bridesmaids or some other woman - which he will likely try to do. You're not being a crazy controlling GF by explicitly stating your own relationship boundaries, and then following through if they are violated. If strict monogamy is one of them, make sure Jay understands that before he accepts Logan's offer.

You want to make a friend regret not having the same feelings you do? She was just being honest. Why on earth would you want to make her feel bad about being honest with you.
Isn't that what good friends do for each other? If anything you should be grateful to her, since she let you know that it's time to stop mooning over her, and start looking elsewhere for a compatible romantic partner.

You invested way too much time in a FANTASY about how great it would be to go out with her, and now you are blaming her for bringing you back down to earth. It sounds to me like your feelings and your pride got hurt when she turned you down, so now you're looking for a way to retaliate and make her feel just as bad as you do. But if you truly cared for her, you wouldn't want to hurt her that way.

A better solution, at least for the short term, is to avoid talking and hanging out with her one-on-one with this girl until you regain your equilibrium. That's a bit harder when you are in the same friend group, but not impossible. In fact, if she tries to initiate a conversation, just tell her "Sorry, I'm not ready to be all buddy-buddy with you yet. Let's give it some time and space." She was honest with you, and you can be honest with her.

I don't think there's any harm in messaging to say you enjoyed catching up with her, and you'd love to renew the friendship if she is up for that. Good luck!