You did fine. Well really. I know this is hard, and you should go ahead and accept the emotions. They are very normal and appropriate.
I want you to try to understand that her leaving is not the end of this. It really isn't. It took me a long time to accept that, but it may be good for your sitch and it may be an absolute requirment to any healing. Think about that. That view is the healthiest way for you to approach this, but it will take some time to get there I'm sure. She needs time and space to figure things out. Give it to her. It will increase your chances of successful DBing.
I know it hurts, but this is not the end. As a wise poster here told me when I was in your exact spot, separation is not the boogey man. There are lots of positives. For one, she is willing to go to MC. Don't feel like you need to start this tomorrow, but it is a good sign. Start it in the next few weeks. Find an excellent therapist - solution based, goal oriented, pro-M.
I have to run for a lunch appointment, but I will check back on you later.
M 39 W 39 M'd 10 yrs; T 14 yrs S7 D4 Bomb 5-8-05 W not working on M 1-22-07; EA 2-22 DB 4-10 S 6-11 No more C Link