Oh boy, I've been in B's place before!
I remember it well because due to a weather emergency (Hurricane Irene), I had to go out of town for work and help with the storm restoration. I wasn't happy about that because it was the first time I was away from my kid, who had recently turned 1. But then, I figured that it might mean I could actually get a good night's sleep. (My kid was the worst sleeper ever.)
Unfortunately, I had to room with somebody from work because there was shortage of hotel rooms. It was a holiday weekend, and also people who had no power for too long were getting hotel rooms.
I found out the first night that my roomie SNORED. At first, I tried really hard to ignore her and sleep, but if was futile. So I wandered around the hotel for a while, went out to my car, and eventually went back to the room hoping that she had stopped. Not so much, and out of frustration I said "Roomie!" and woke her up by mistake. She said "what?". I asked if she knew that she snored really, REALLY loud? She had no idea! Apparently, her SO sleeps with a CPAP mask, so he doesn't hear anything.
Anyway, after I woke her up, I actually did manage to go to sleep for a short while. The next night, we stopped at CVS and I bought earplugs. We didn't have the option of splitting up because of the shortage of hotel rooms. The earplugs, coupled with the 2 drinks I had that night, really helped me sleep.
Roomie felt horrible about the first night, but we do joke about it now.
B should have tried to find some other option before moving to another room and asking A to subsidize it.
ETA: Oops! Got A and B mixed up. Thanks DottyG for pointing it out!