Ultimately, everyone needs a way to vent. Having someone that you can unload to is invaluable. Think of it as a cheap alternative to psychotherapy. When she's done talking about her day, she's probably feeling a sense of catharsis, and doesn't want to ruin it by dealing with your day.
Try waiting until some other time to tell her about your day. You can't both dump on each other at the same time; it just doesn't work, as you've already discovered firsthand.























