After she becomes the Bad Wolf there is a part of her that, for lack of a better word, is fucked up. She tries to go back to being the Doctor's perfect little flower, but it seems as though there is something inherently wrong with trying to force herself to be that girl again. She gets used to the new Doctor, and puts forth a reasonable front, but it's at night that the wolf cries for freedom.
She wakes up in a library, one they never use, torn books scattered around her. Another time she is in the console room, her fingers far too close to the controls for comfort, the dial set to the end of the world. She stops wanting to leave the TARDIS, though she doesn't tell the Doctor. She feels restless away from the ship, and when she's there she stops sitting in the library with him or making tea at odd hours. Instead she curls up in the jumpseat, just watching the console for hours on end.
He is worried about her, she can tell. She screams at night, bringing him to her room. She never tells him what she dreams, but the future is in her mind, warning her of death to come. She stays close to him, never telling him that she will die. Eventually the nightmares get so bad that she stops sleeping, and he stops asking.
By the time they go to visit her mum she is falling apart. When she ends up in the parallel world, feeling like death itself, she can think nothing but of course. She begins fighting to return, but it's only when the wolf takes over that she makes any progress. Every time, though, it's harder to become herself again, to remember who Rose Tyler is.
When she returns she doesn't expect to walk right into the Doctor. She isn't supposed to still love him even when he's an old man, but she does. She leans through the bars, holding his hand. The instant their hands touch, overjoyed, Rose dies, for real this time.
"I am the Bad Wolf," she whispers, every word teeming with power.
The Master enters the room and looks at the blonde girl with glowing gold eyes. "Rose," the Doctor whispers, but it's too late.
The Bad Wolf crosses the room to the Master. She tilts her head and says, "I can control the TARDIS."
The Master looks into her eyes. "Are you really going to leave him behind?"
"Time is corrupt, is it not, Master? Rose and I simply look for forever." She knows that her words have wounded the Doctor, and she wears that knowledge with pride. She says two more words to the man she was in love with. "Doctor, I—" and then she is gone, her work done and her host avenged.
Rose Tyler, the Bad Wolf and the Master in the TARDIS, just as it should be. Too bad one of them is dead.
I am so sorry that I've been absent since, um, January. Thank you for sticking with me. I hope you enjoyed this, and please review!