Alpais Lam Wai-sze posted a message on the internet on Thursday confirming the speculation, saying that she was "scared".
Police said the complaint was made by a 59-year-old man who said that Lam could have broken laws with her disorderly behaviour in public and for obstructing officers in doing their duties.
The man - whose last name is believed to be pronounced "Lee" - filed the complaint based on footage he saw on video-sharing sites, and reports in the media.
At a public forum last Sunday, Chief Executive Leung Chun-ying ordered the Education Bureau to submit a report about the incident. The request has sparked criticism from both the public and education sector.
Secretary for Education Eddie Ng Hak-kim said on Thursday that the bureau had asked Pui Ling School of the Precious Blood - the school in Fanling where Lam teaches - to write the report.
"The school's management and board of directors are expected to hold meetings to study how to best handle the case," said Ng. "They are going to file a report to the bureau. The report will offer an updated and holistic view of the whole incident."
Lam, as a bystander, was filmed swearing at police officers when a scuffle broke out between Falun Gong and the Youth Care Association on Sai Yeung Choi Street on July 13. She was not happy with the way police handled the case.
The video was then widely circulated on the internet, sparking debate on whether the teacher gave "an appropriate" response at the time. The video also prompted a pro-police rally on August 4, organised by the Parents' Association of Hong Kong and Hong Kong Action. On that day, another scuffle broke out on the same street between hundreds of Lam's supporters and critics.