How would you react, if your SO wanted separate bedrooms after marriage?

My GF of over 2 years recently told me, that she wants separate bedrooms after we are married/live together. I was stunned by this and just said ?why??. She said she needs to be alone in the evenings and do her things when she is about to sleep and make herself comfortable. Sleeping next to anyone is not doing that for her. I said it?s extremely important for me and I don?t want to sleep the rest of my life in a lonely bedroom by myself. Her answer was ?well then you can look for somebody else if that is what you want?, as if she already knew I wouldn?t break up over this.
But now a few weeks later it got me thinking, would it be a valid reason for other people to break up over this?
(We slept in the same Bed multiple times before, but not often)


Source.