Maybe the best thing you could do is remind her that this weekend isn't the be all and end all and that whatever she decides, she should remember that everyone will be ok and there will be new fish to fry as there always is...
I don't get why I would say this? Not saying its wrong, just don't understand.
I really the need the why when it comes to putting this stuff into action.
Isn't it true? Aren't you both obsessing as if this is the final frontier. It's not. Do you want it to be. Is this ultimatum time. If you go with him, we're through...oopsy, you don't have that leverage anyway, do you?
Tell her to make her own decision and you don't want to be involved. Or don't say it in words, just live your life, let her make a decision and do what you need to do.
Seriously, this is becoming so symbolic and that is why she's stressing out and so are you.
Be cool, remember, you're the cool guy, you've got your sh*t together unlike Mr. Pressure Pants who has to bully a woman to be with him. You just sit back and let the ladies come to you...