I'm sorry you are hurting.
The month isn't over, she broke up with the cheater. Pray it sticks and she starts coming back to Earth.
That said? Even if her lover had NOT BEEN a cheater person? That doesn't mean you wouldn't have gone through some of the poly hell
It is that in your case -- you get to have a double whammy. The "poly hell" feelings of change and transition PLUS cheater UGH side helpings magnifying it even bigger.
I see you are disappointed that the anniversary celebration you planned doesn't seem likely.
Could remember and keep in mind that your union is not about "remember the wedding day" -- it is about the union and recommitting to the union. Or at least it is in my book. Marriages have to be TENDED.
So skipping anniv. celebratory things like eating frozen cake or gifts to do the work to resecure the union? That takes priority and is more helpful to the endurance of the union than any mixed tape could ever be.
Could reconsider therapist appointment. You may feel tired, and you may feel blah, and you may feel grief and sadness. But making an appointment demonstrates your willingness to keep trying to resecure the union even through your pain. Then chill til appointment time rolls around.
You guys Opened without having all your communication business sorted out well. You could consider this is a second chance for all -- not just to heal from this, but to make a BETTER plan if you ever decide to try to Open again in future.
If you no longer want to be in the marriage, that is fine, and your right.
But if you do still want to be in it... BE IN IT.
There's no halfsies in marriage. You are either doing behavior that is moving toward your spouse or doing behavior that is moving away from your spouse. Feel whatever it is -- cry if you want to along the way. But emotions are just emotion. Sun is sun, rain is rain. Internal weather blowing on through here is just internal weather.
Don't not do correct behavior because of yucky weather. Get an umbrella and get on with the business of the day.
Could figure out what "correct behavior" for you today is. Could choose what behavior you want to be doing at this juncture, TODAY. Behavior that moves toward your spouse or away from your spouse?
Hang in there.