Roommate drags friend into conflict with girlfriend

DEAR HARRIETTE: My roommate and his girlfriend constantly bicker, and I always end up being dragged into the middle of their arguments. It’s frustrating because I feel like I’m being forced to pick sides when I don’t even want to be involved at all. To make matters worse, I can’t help but feel bad for his girlfriend because, frankly, my roommate is wrong most of the time. He’s selfish, dismissive of her feelings and stingy when it comes to sharing expenses or treating her to a nice date. I can tell she’s unhappy with how he treats her, but for some reason, she stays with him.