Tituba does not want to name others as witches. When she does so, it is because she sees no other way to save herself. Tituba tells them she does not work with the Devil, but they do not believe her. Unless she confesses, she will die.
Tituba: I have no power on this child, sir.
Hale: You most certainly do, and you will free her from it now! When did you compact with the Devil?
Tituba: I don’t compact with no Devil!
Parris: You will confess yourself or I will take you out and whip you to your death, Tituba!
Putnam: This woman must be hanged! She must be taken and hanged!
Tituba, terrified, falls to her knees: No, no, don’t hang Tituba! I tell him I don’t desire to work for him, sir.
She realizes denying seeing the Devil does her no good, so she says she saw him with others. When they ask who she saw, her first response is "I don’t know, sir, but the Devil got him numerous witches." They keep pressing her and ask her leading questions. This means they basically give her the answers, telling her what they want to hear.
Parris: Who came with him?
Putnam: Sarah Good? Did you ever see Sarah Good with him? Or Osburn?
Parris: Was it man or woman came with him?
Tituba: Man or woman. Was—was woman.
Parris: What woman? A woman, you said. What woman?
Tituba: It was black dark, and I—
Parris: You could see him, why could you not see her?
Tituba: Well, they was always talking; they was always runnin’ round and carryin’ on—
We can see that Putnam specifically asks about Good and Osburn.
Tituba's lines demonstrate that she does not want to name someone else. She tries to say she couldn't see who it was, but the men are relentless in their questioning. They will not rest until they receive a name. All of her answers are simply what they have already said; they ask if it was a man or a woman, so she responds "woman." Hale asks "Who came to you with the Devil? Two? Three? Four? How many?" So Tituba tells him "There was four."
Despite saying there were four of them, Tituba only gives two names: Good and Osburn. As noted, these are the names that Putnam has already suggested. Tituba doesn't pull these names out of nowhere. In order to save her own life, Tituba tells them what they want to hear.