Let me begin by answering the questions posed in the revision post.
Is the ruthlessness just a front for actions that make her feel uncomfortable, or does she genuinely not care?
Deep down UAD is a fancy term for psychological repression. The notion that the dead are rising is something so completely insane, so unreal that individuals who suffer from it have difficulty coping with reality. Is her ruthlessness a front for actions that make her feel uncomfortable? Yes, but she has no other coping mechanisms beyond being particularly violent.
Carla was raised in a family where feelings weren't normally "discussed" or acceptable. Her father was raised in a school where "anything" was possible on the job and anything could happen. Therefore being unable to cope with shooting down the rotting corpses of several major hollywood stars along with individuals at a Halloween Haunt in Griffeth Park who had been bitten and turned had a major effect on her.
However, Carla was raised strong and grew up strong. The fact that something happened which she is unable to explain or feel comfortable about cannot bother her. Her mind shuts it out because facing up to it and the actual fact that vampires, werewolves, and zombies are real would break her.
That thought terrifies her. Carla doesn't have a lot of fears, but not being taken seriously and losing her reputation is one of them. That, coupled with the way she was raised in a hard house is what drives her actions and contributes to UAD and her ruthlessness. She does whatever she has to do to survive because she knows that if she doesn't people might see her as weak and her real nature will be exposed.
It's easy to assume that, growing up in a family full of cops Carla didn't have much of a feminine childhood. She knows how to be a girl and dress as a girl and act as a girl but she was equally encouraged in sports and other activities. She has never seen the difference between girl feelings and boy feelings-apart from their physical differences-until she was first confronted with situations that led to a feminine response. Her UAD is a direct result of her being unable to cope with her problems and-when confronted with something that causes an emotion she'll repress it and become twice as ruthless.
In short. Is her behavior a front for her own insecurities? Yes. When confronted with things that instigate further emotion (something she sees as "insecurities coming to life") she would become more hostile and ruthless.
This problem has been brought to her attention. While it's not something that she ignores it is something that she feels would inhibit her job on the boat. Therefore it is something she will be keeping to herself, unless her inmate requires it.
Does she resent having to be polite when it's expected of her, or is she a real team player?
Carla was raised in an environment that was connected and warm. She grew up wrapped in procedure with a large extended family. She is by nature a team player...with the right kind of team. Carla comes from a line of blue-collar workers. They're used to dealing with their own kind, namely other blue collar workers. Carla is used to playing with the team but does not respond well to other authority over said group. Her view is that if you have authority, then you have to earn it one way or another.
By rising up through the ranks of the team.
This is a behavior she's inherited from her father and her mother. For example, while she respects Captain Dashell, she takes his orders with a grain of salt as authority. As the series progresses, he earns her respect despite being a goofball. While she won't be overtly hostile to people who she does not respect but who have power-she does not want to have prolonged contact with them. This is shown in regards to the Lt. from HQ who starts the "PUS system." She honors him for his badge-but does not respect him personally. When he is bitten, she happily tortures him by reading off his card before shooting him in the head. Black comedy at it's finest.
In summation. Carla is a voice of authority and takes the lead for only as long as it takes for her to find someone else who can take the lead and act as a voice of authority. She is a perfect Beta dog. Like most beta dogs however, you need to earn her respect before she is willing to relinquish authority to you.
Every single person who she works with has earned her respect (apart from Kristen but that comes during the series.)
Carla gets anxious when she doesn't have individuals who she can trust or rely on. The first few days/month will be hard on the barge for her as she'll be learning the lay of the land and probably latch onto people who will. Consequently, she might put a few people off or be rather quiet and then show off her skills to get "in" or "make friends".
She knows this is a prison. She will also probably approach the barge a bit more traditionally UNTIL she learns the lay of the land.