In The Crucible, does Mary Warren deny that she made poppets?

No, she does not. When Ezekiel Cheever and Marshall Herrick come to the Proctor's house to arrest Elizabeth, they specifically come to find a poppet. Abigail Williams had accused her of witchcraft and had that evening cried out in pain whilst at dinner in Reverend Parris' residence. On investigation, a needle was found stuck in her stomach. Abigail claimed that Elizabeth had sent out her spirit to harm her and had stabbed her with the needle.

Cheever has been sent to find this evidence. When he sees the doll Mary has given Elizabeth as a gift, she tells him about its origin and that she 'kept no poppets.' Mary is summoned to verify what Elizabeth said and the following extract is the gist of her testimony:

Proctor: Here now! Mary, how did this poppet come into my house?
Mary Warren, frightened for herself, her voice very small: What poppet is that, sir?
Proctor, impatiently, pointing at the doll in Cheever's hand: This poppet, this poppet.
Mary Warren, evasively, looking at it: Why, I - I think it is mine.
Proctor: It is your poppet, is it not?
Mary Warren, not understanding the direction of this: It - is, sir. Proctor: And how did it come into this house?
Mary Warren, glancing about at the avid faces: Why - I made it in the court, sir, and - give it to Goody Proctor tonight.
Proctor, to Hale: Now, sir - do you have it?
Hale: Mary Warren, a needle have been found inside this poppet. Mary Warren, bewildered: Why, I meant no harm by it, sir. Proctor, quickly: You stuck that needle in yourself?
Mary Warren: I - I believe I did, sir, I - 

Mary goes on to explain that she has not been conjured into saying what she does, on a question from Reverend Hale. She says that Mary Walcott and Abigail Williams saw her sewing the doll and that Abigail was sitting right next to her at the time.

At this point, John Proctor demands that the Reverend Hale ask Cheever to leave for there is no justification to arrest Elizabeth. Hale then accuses Mary that she has just condemned Abigail on a charge of murder, which Mary denies. It is at this point that Elizabeth is told by the reverend that she has been charged by Abigail for having harmed her with the needle.

Elizabeth's passionate response that Abigail is a murderer and that she should be ripped out of the world is what spurs Cheever to continue with the arrest. The outcome is that John Proctor tears up the arrest warrant but Elizabeth beseeches him to be calm and allow her incarceration. She then leaves with the two arresting officers, who put her in chains, much against her husband's will.