I CAN'T stand when people are in a funk and bring down the mood.
Your friends don't get to be unhappy around you? That seems like a pretty thin friendship. People have feelings, sometimes they're going to express them and if you've told her this many times and then asked if she wanted to do this some other time, she had to know what was up. I would want a friend to listen to me gripe, agree with me that the other people were all effing idiots till it was out of my system, and then move on and have a good night.

If she's someone who stomps around being a jerk and milking it all the time, that's one thing, but it sounds like you just don't want your friends to be unhappy around you, to suck it up and put on a happy face and not infringe on your good time and that's not being much of a friend. Bad things happen and it's normal and ok to react to them.

I'm not a big emotional outburst person myself, but I know it's appropriate to be unhappy or angry sometimes and people need to work that out. Granted, I don't want to hear about someone's credit card mistake for HOURS but I understand if they need to be pissed for a while to get past it.