Hoping to still move forward, huge setback

[chasingpavements]

Yes, that makes sense. I think you have set a good and reasonable boundary that you would not like her to be around him when you are not around. That is perfectly reasonable and understandable. I would feel the same way. Hopefully you can deal with some of those issues at your MC. Hopefully you can express to her that you have been hurt by her actions and that you will require some reassurance from her over the following months as it will take time for you to heal after what happened.