Twenty-one-year-old Danielle Blankenship told Boulder Police she would never hurt the cat and did not smoke heroin.
Her ex-boyfriend made the allegations to Boulder Police Tuesday. He also claimed Blankenship hit him.
When officers arrived at his apartment to investigate a domestic violence complaint, they noticed the male cat, Muffin, at the bottom of the stairs.
"It was breathing, but not moving," Boulder Animal Control Supervisor Janeé Boswell said. "At that point, I picked the cat up to see if it would walk. It took about a step and it went limp and it tumbled over."
Boswell says she went outside to get a carrier to take the cat to the veterinarian.
She said when she returned, "One of the police officers advised me that the boyfriend had made the statement that the girlfriend blew heroin smoke in the cat's face."
9NEWS tried to ask Blankenship about the allegations at her apartment near the University of Colorado campus. She did not come to the door, only saying she has hired a lawyer.
Blankenship did tell police she never did drugs, but did smoke marijuana, according to the police report.
She also said she would never hurt the cat.
"We see cruelty incidents every day," Boswell said.
For this incident, if heroin was actually in the cat's system, "An act like that comes from somebody who's ignorant," she said.
Toxicology and necropsy results are due next week to determine whether heroin was actually in the cat's system.
Blankenship faces charges of misdemeanor animal cruelty and third-degree assault.
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