Dawn Nguyen of Greece was arrested Thursday afternoon at a home where she and her mother, Dawn Welsher, were staying, The (Rochester) Democrat and Chronicle reported.
State Police Senior Investigator James Newell said Nguyen will have a court hearing Jan. 8 on a felony charge of first-degree falsifying business records. He said the hearing will be in Henrietta Town, where the guns were bought.
Newell said an unspecified federal charged also would be brought against her.
Nguyen's attorney, Dave Palmiere, said Friday his client "purchased the weapons legally, and they were stolen." He said she didn't recall whether she had reported them stolen, the newspaper said.
Palmiere said the charges were related to a .223-caliber Bushmaster rifle and a Mossberg 12-gauge shotgun, not a handgun also found in the possession of William Spengler Jr.
Investigators said Spengler, 62, of Webster, laid a trap for emergency personnel who showed up to fight a fire that eventually destroyed several houses.
Welsher, a former neighbor of Spengler, had left a voicemail with a Democrat and Chronicle reporter saying she wanted to talk.
"This is nuts," she said. "I never supplied this man with nothing. My daughter never supplied him with anything. He's setting us up."
She subsequently told the newspaper her attorney advised her not to speak to the media.