Sleeping in another room, looking at that empty master some nights is not going to get easier.
Let her redecorate a guest room, if she chooses to visit as a guest. Redecorate your master as if you are the master who will continue to live there.
It does sound contrary to what you are feeling. It may sound like it will disturb her.
Uhh... she is disturbed and that won't change soon. Limit how much you become disturbed. See a professional and discuss these things. Find your strength. Ok, don't redecorate the master, but live in it. No matter what you try right now, you will have the ups and downs of life on the roller coaster. Try to make your seat safe and comfortable. Don't give away leverage over your life to someone who will not appreciate or honor it.
If she has a place to go hide there is no reason for you to need one. That is her way of trying to slip you out the door. No way. You don't need a "room" somewhere else when you have one you aren't using in your home. Your call, not hers.
If you really want a middle ground, then explain you will only sleep in the guest room when she is there. Where you sleep when she is out, is up to you. If she wants to move you out of the master, she will need to do it one night at a time, by being there.
