Oh, and don't fall for the "I am taking the high road, and am the victim" act that your wife portrayed by calmly getting the pillow.
The choice to end the relationship and move out of the family bed was hers. She could have made different choices, but this is the one she made. You should not feel any guilt for allowing her to make this choice.
She doesn't have the right to tell you were you have to sleep. You get to decide where you sleep, she gets to decide where she sleeps. It is that simple.