My understanding of the process and the reaction to it is generally this:
1) Venom is injected.
2) Pain is excruciating, like being burned alive.
3) Person loses all sense of self due to the pain.
4) Screaming and thrashing is expected.
4) A measure of self-control gradually returns about halfway through.
Per Rosalie, it sounds like the same thing happened to her as it did to Bella, in that about halfway through her brain had become vampirized enough that she was actually able to begin thinking again and consider the fact that screaming did no good. Presumably, she likely stopped when she had gained sufficient control, or at least had it somewhat under control.
Bella even makes something of a childbirth analogy, even though her experience was particularly bad:
- The baby, kicking my ribs apart, breaking her way through me piece by piece. That was nothing. That was floating in a pool of cool water. I’d take it a thousand times. Take it and be grateful.
So, what she is describing is incomprehensible to us. People do handle pain differently, but what Bella is describing is outside of our experience; at least, those who do undergo that type of pain, being burned alive at the stake, only endure it for moments before dying.
Vampirization of the brain allows the person to regain consciousness of the outside world (time restarting) and with that the beginnings of self-control. As Bella puts it, she is finally able to start thinking around the pain, so that the pain is no longer literally all-consuming.
This was my understanding,
Grayce. When you say "as quickly as she realized why she couldn't", that would apply to everyone at the point they began to have awareness again. Bella maintained her silence for the last half, which was extraordinary, but she was hanging on by a thread and knew her body would betray her if she had to respond to Edward in any way. She at least had a reason for not crying out.
- "Bella? Can you hear me?”
I knew, beyond all doubt, that if I unlocked my teeth I would lose it--I would shriek and screech and writhe and thrash. If I opened my eyes, if I so much as twitched a finger--any change at all would be the end of my control.
Granted, everyone is different. But if Bella knows she will scream out unless she maintains absolute focus, then the implication is that everyone screams or thrashes about since they have no earthly reason not to. And this is a Bella who is getting stronger with vampiric self-control, but still right on the razor's edge of losing it.
And at the beginning of the change:
- I knew all the stories. I knew that Carlisle had kept quiet enough to avoid discovery while he burned. I knew that, according to Rosalie, it did no good to scream. And I’d hoped that maybe I could be like Carlisle. That I would believe Rosalie’s words and keep my mouth shut. Because I knew that every scream that escaped my lips would torment Edward.
Now it seemed like a hideous joke that I was getting my wish fulfilled.
If I couldn’t scream, how could I tell them to kill me?
All I wanted was to die. To never have been born. The whole of my existence did not outweigh this pain. Wasn’t worth living through it for one more heartbeat.
Let me die, let me die, let me die.
And, for a never-ending space, that was all there was. Just the fiery torture, and my soundless shrieks, pleading for death to come. Nothing else, not even time. So that made it infinite, with no beginning and no end. One infinite moment of pain.
First, Bella wants to scream. She wants to be killed, it's too much.
Second, she appears to lose all sense of self and of self-control. All she knows is pain, and all she wants is to have it stop.
So, at the beginning when she undergoes the change she would have screamed out if she could have, and she wanted to, she wanted to die. When she begins to regain self-control she still wants to scream out, except Edward is there and she is aware of it and not screaming out has some meaning to her.
All of that is to highlight what Carlisle went through, which appears to be
utterly unique. He was at least silent enough from the very beginning not to catch the attention of anyone in his village who was conducting a search. He may have made some noises, but not much. He maintained enough control at the beginning to actually seek out a hiding place.
As far as I know Carlisle is the only one who did not scream out from the very beginning. And, he was able to either maintain some kind of consciousness, and therefore self-control, sufficient to not cry out, or he simply didn't even as he was overwhelmed with the sensation of being burned alive for hours on end. Halfway through the process his self-control would have improved, just as it did for everyone else, but it is those first hours that are remarkable. It wasn't that his self-control finally came back to him, it's that it appears
he never lost it.
Carlisle's self-control, therefore, does appear to be something I might call a supernatural talent, since he is the only one that demonstrated it to the extent he did. I said before that there is a contradiction there, Carlisle not crying out at the beginning, when everyone appears to have done it. Maybe that isn't a contradiction, that simply demonstrates that this self-control is a manifestation of a natural gift no one else has.
It makes me hurt for them. I guess if you've never been around it or exposed to it on a daily basis, you may not be able to smell it in a room unless you knew what it was. It just seemed for the books at least, that it was special ability for Bella to be able to smell blood even before she was turned. That's what I found odd about it, not that she could do it, but that Edward at least thought humans couldn't normally.
Maybe not the same thing but in reference to long term constant pain, I've had 5 kidney stones. I think that would rank right up there. At least with childbirth, you have something cute to show for going through 2 days of pain. 
