Hiya!
[MENTION=6854554]Proto[/MENTION], I hate to suggest this...as some groups degenerate
instantly...but...when something comes up "what would your character do?" type of scenario; take that player out of the room and into another.
I think what is happening is that the other players have gotten used to the dominating girl as "unless I strongly object, lets do what she wants". Or, sort of a "learned behaviour" type thing. If the dominating player type isn't at the table, then each player doesn't have that 'crutch' to fall back on and they have to make their own choices and live with their own consequences. Once each player grows a backbone, so to speak, you can do it less and less to the point of where my group and I are at. My players do what they think their character would do...even upto the point of dileberately putting another character's life in danger (if it is in-character to do so...doesn't happen very often, but it does happen). If, after a few of these little "incidents", neither character is dead, one of the players will introduce a new character and the old one that "didn't get along with X" leaves. Because, well, that's what would happen in real life. If you don't kill someone you hate at work, you or he/she usually end up leaving or getting fired. Adventuring groups tend to be surprisingly similar in psychological make up...hmmmm....there's a study in there somewhere! "
Hey, government? Give me a grant to study RPG'er psychology for a few years!"...
As for how to get the
players to actually think from the perspective of their
characters... that's a bit more tricky. Some people just don't really like that part of the game...others love it. When you have someone who loves it and someone who could give a wererats rump about it sit down and play together. Well, sparks fly for a bit, then it evens out and both sides compromise.
That said, I am running a
Masterbook RPG campaign right now called
Zombocalypse!. Yeah, zombie-survival. It is, basically, a reworked "
State of Decay: Year One Survival Edition" video game, but put to paper. One of the things I like about SoD is that it has a "Community Morale" meter that goes up and down based on your actions and what psychological make up each character has. A "Total Lush" (re: drunkard) will frequently get into shouting matches with someone who is "A Team Player". Someone who is "Kind Hearted" will not like someone who is a "Psychopath". To that end I made each player choose two "core psychological traits"; one 'good', one 'bad'. I implemented a "Colour" (a basic 'alignment' type thing) for each PC/NPC. The farther away your colour is from another, the more an adjustment to Difficulty Number's would be. The same colour and you get a bonus. They typical "Roy G Biv" colour scheme everyone learned in kindergarten is used (Red, Orange, Yellow, Green, Blue, Indigo and Violet). Each difference is a 2 point mod, so a maximum of -6.
Ahem. I digress. The point is that I'm giving in-game mechanical adjustments based on character traits. This could be done in a slightly more loose form for 5e. You could give bonus XP (for role-playing) as an added incentive. In this way, each player has two 'traits' to latch on to when role-playing. I THINK this was the general intent of the whole "Background" thing...but I was surprised there wasn't more "mechanical meat" to it as an option in the DMG. As a purely RP choice thing, it's perfect. No requirements, no advantages or penalties other than the almost-never-used "Inspiration Dice" mechanic (I'm still not sure how to use that in my 5e games...).
Anyway, long in the tooth post here, sorry. Another option is to take a serious look into Precis Intermedia Games "Plot Development Cards" (
http://www.pigames.net/store/product_info.php?products_id=809 ). They focus on story/plot, not characters per se, but they have a lot of very character-based results. Like
"A family member appears. (INSPIRATION; Who is the family member? Whose family? Why is he here?)", or
"Someone is stalking a character. (INSPIRATION; the stalker could be a person, animal, spirit, or not really there. Why is the stalker doing this? Does the victim know about the stalking?)" These cards pretty much lead directly into player character 'psyche' as the GM and Player collectively work out the details in an organic, free-flowing type of way. We love these cards...hell, we love the regular "Drama Deck" cards for use in Masterbook (same web site...at top, under Catalog, look for Masterbook). Those are a LOT of fun and really add to the game, IMHO. I'm stunned why this didn't catch on when they were first introduced back in TORG days (iirc). When a player 'plays' a Plot Dev card, they get a Life Point (think of it as a "Hero Point"...not a 'hit point'...as in "This Point can save your Life")/
Sorry again for the rambling. Key: Players need to be weened from relying on dominant players (player), psychological traits should be written down for character, mechanical incentive to RP those traits.