You know, she may actually miss you when she's gone. She may need distance to see what she might walk away from.
I'm sorry it hurts so bad. I've been there.
You can't control her if she wants to leave. And remember your 180's - if you have done a lot of trying to convince, explain, say ILY, etc. she expects you will do this. If you shut her out and only focus on you - if you let her go - she may have a shock on her hands. It's easier for WAS to walk away when one person is holding the R together. If you truly let he make her own decision, she has to hold the part of the R that was good, has hope, etc., too.
You will find that place inside you that is ok even if she goes. There is that inner calm place in you of acceptance somewhere. It will just take time to find it.