Choi returned to South Korea early on Sunday from Germany, where she had been staying, and was ready to answer prosecutors' questions, her lawyer said earlier.
Aside from saying sorry to the nation for secretly leaning on Choi's advice, Park has responded with a reshuffle of senior secretaries and other aides.
Citizens and academics, however, expressed doubts that Park would face impeachment as it requires approval of the president-appointed Supreme Court.
That kind of influence has some critics comparing Choi to Rasputin - much like they did her father.
Almost 30,000 South Koreans gathered in downtown Seoul Saturday to demand that President Park Geun-hye step down from her post, the result of an ongoing scandal involving Park's friend Choi Soon-sil. It is unclear if there will be any details revealed from her meeting with prosecutors.
The senior government official who later shot and killed Park's father, the dictator Park Chung-hee, is said to have claimed he staged his attack in part because Park Chung-hee would not keep Choi's father away from the young Park Geun-hye. The banner reads, "Call for Park Geun-hye to step down".
Chaos ensued as Choi said she had "committed an unpardonable sin" as she begged for the forgiveness of the Korean people.
An unidentified man was taken into custody after dumping a container of what appeared to be animal dung at the door of the prosecutors' office after Choi went in, demanding that prosecutors undertake a proper investigation.
Presidential spokesman Jung Youn-kuk told reporters on Monday the government will maintain a "firm readiness posture under any circumstances".
Ms Choi is the daughter of shadowy religious cult leader, Choi Tae-min, who was Ms Park's mentor until his death in 1994.
Justice Department advised FBI against Clinton email letter
The computer was shared with long-time Clinton aide Huma Abedin, Weiner's ex-wife. Before it's here, it's on the Bloomberg Terminal. Another 1% said they had no opinion.
Choi said she received the draft speeches but denied she had access to other state documents and said she did not influence state affairs nor reap any benefits.
But the tipping point that led to the (local time), was the emergence of a woman named Choi Soon-sil.
Rumors swirled at that time about Choi suspected of using his connections to Park to commit wrongdoings in the joint management of pro-government volunteer groups.
President Park's efforts to extricate herself from this crisis by apologizing and firing officials that may have facilitated Choi's involvement have not eased public outrage. Legal experts say that if Choi is found guilty, she could be facing serious penalties.
Choi is the daughter of one of Park's earliest political backers.
There are allegations that Choi was influential in setting Park's hardline positions to reject any engagement with North Korea, to close the jointly run Kaseong industrial complex after the North's nuclear test in January, and to agree to deploy the American THAAD missile shield over the objections of Beijing. All of the "problem figures" in the Blue House were replaced Blue House Spokesperson Jung Youn-kuk announced that Park had accepted the resignation of several key Blue House secretaries on October 30: Chief of Staff Lee Won-jong, Senior Secretary for Policy Coordination Ahn Jong-beom, Senior Secretary for Civil Affairs Woo Byung-woo, Senior Secretary for Political Affairs Kim Jae-won, and Senior Secretary for Public Relations Kim Sung-woo. So far, five senior aides have resigned.
Opposition parties have demanded a thorough investigation, but have not raised the possibility of impeaching her.
It is ironic Park had proposed amending the constitution to allow presidents to serve multiple terms just a week ago. "Although I'd say it's unlikely", says Strother. Her televised apology sparked intense criticism about her mismanagement of national information and a heavy-handed leadership style that many see as lacking in transparency. They have surfaced in the past when scandals hounded presidents, before eventually fading.
At the same time, it will be hard to force President Park from office before her term ends in 2018.