To be honest it sounds like the wrong group for her. And probably the wrong game. You've a table of gamers, focussed on the step on up style of play, and one basically freeform improver who wants something a lot more character driven.
I think the problem is that she is the "odd man out". She wants more story-based, social skills, skill challenge play. The rest of the table, it seems, does not. And their playstyle has been "the game" for how many years? In my games, there is more of a balance, but in my games storming the city gates is likely to be fatal - a small band of adventurers isn't powerful enough to take on a city, or a castle, and many problems cannot be solved by combat.
If you're going to insist that the game you and your players have enjoyed for years change markely to accommodate her playstyle, I expect you will be accused of favortism. I'd also think that may be fair - would you be arguing for similar changes to the group playstyle if the new player were not your girlfriend?
This does seem like a basic clash of playstyles. A group that has been together for that long and used to playing in a certain way isn't likely to change the way they play for any newcomer. Its always tough when gaming styles clash and especially difficult when a SO is involved.
In defense of the wife, it sucks to be part of a group that ignores your contributions and preferences.
In defense of the old guard it sucks to have an established way of doing things suddenly upset by a newb that won't get with the program.
I think I need to clarify a few things.
First of all, my girlfriend is not a "newb." She has played D&D for nearly 20 years, having started with AD&D back when she was in high school. Like me, she has been both a DM and a player. The ones who are newest to the hobby are two of the other guys at the table; they had only played 3.0E back when it first came out in 2000. Even so, we have all been playing D&D off and on for at least a decade.
Second, she is not a "newcomer" to this particular group either. We all started this campaign at the same time, when a group of friends were chatting at a party, discovered that we all enjoy playing D&D, and asked me to be the DM. They all rolled up Lv. 1 characters at the same time, and went through the first intro adventure together. That was back in October of 2011. Everything was going fine up until a few months ago.
Not all of our girlfriends are newcomers to this hobby.
Lastly, there is no confusion about whether or not we are playing the "wrong game." D&D is nothing if not flexible, and I have seen it played in many different styles through the years. The way we play D&D does not require us to choose deep roleplay over powerplay, or vice versa.
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I did what I said I would do; I spoke with them all privately before the next gaming session. I asked them what they thought had happened in the group over the last few months that might cause this rift, and what they think should be done to make it better. Here is what I learned.
I had a really good chat with the first guy, over lunch (we work together). We talked at length about the game, wondering aloud about what had happened and what could be done better. He noticed the shift in playstyle too, and that he thought it had more to do with their characters' levels. Back when they were all low-level characters, combat was a lot more risky and limited, so they had to resort to skill challenges in order to survive. But now, they are all 12th and 13th level, and death is more of an annoyance thanks to Raise Dead and other effects. They also have a lot more combat options, too: new weapons, new abilities, new spells, and so on, that they are just itching to try out. Skill challenges, he said, feel like a waste of time now that there is "cooler stuff" that they could be doing. As for making it better, he got really uncomfortable and changed the subject.
The second guy I spoke to was a live wire...he seemed like he had been waiting for this opportunity. He blamed me for the rift, saying that the difficulty level of their skill challenges is not proportionate to the difficulty level of combat. (A CR 10 trap, he said, is a major challenge that could wipe out the party...but a CR 10 monster is a pushover...they don't want to do skill challenges anymore because they are too hard.) He suggested I curb the difficulty of the skill challenges drastically, or just handwave them. "Every character in the group is built for combat, not skill challenges," he said, "or didn't you notice?" He went on to complain about other stuff, like save-or-die spells or the confirmation roll for critical threats, but in all honesty I could barely listen to him after that "didn't you notice" comment. It was all I could do to remain polite.
The third and fourth guys didn't have anything to say at all. They said they didn't notice anything very different about the gaming sessions in recent months, and they each thought that the argument at the last gaming session was not that big of a deal, or that it was blown out of proportion. (The third one didn't remember an argument at the last gaming session at all.) I know that these fellas don't like confrontation, so I didn't pry. I got the feeling they just wanted to put this whole mess behind them, and get back to playing.
My girlfriend expressed fatigue more than anything else. "I'm so tired of you having to fix this stuff," she said with a smile. "Doesn't it get exhausting?" She blamed herself for the whole mess, but wouldn't elaborate. As for making it better, she said that it wouldn't get better until she left the group, so she would drop out. I tried to talk her into just taking a couple of gaming sessions off instead of quitting the group outright, but she didn't go for it. She gave me her character sheet and asked me to make her paladin an NPC. She said she might start an AD&D Ravenloft group of her own in a few weeks.
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Tonight's gaming session was rough...it was clear that there were still a lot of hurt feelings at the table, on both sides of the DM screen. But not much else has changed, I'm afraid. Instead of getting off-handed comments about my girlfriend, bias, and favoritism, I get off-handed comments about martyrs, retribution, and vengeance. I'm sure they were just trying to be funny, but I wasn't quite ready to laugh about this yet. So I smiled and joshed and tried to make light of the situation, but my girlfriend was right: it is getting exhausting. I hope this phase passes quickly.