How to manage personal space when WFH

My GF and I both work remotely, we each have our dedicated workspace(rooms) for our office. While I try my best not to disturb her while she is working, she constantly walkes into my office, stands there and demands my full attention with some random minutia. I also do day trading, which means I can lose a lot of money if I'm not paying attention. Am I wrong for wanting personal space while working or am I being selfish?