One of the founding members and the last remaining abuse survivor on the Pontifical Commission for the Protection of Minors has quit over what she described as resistance coming from Vatican offices against implementing recommendations. He also stresses her desire to continue working with the Commission, as well as with the Centre for Child Protection, for which she has agreed to do a video, recounting her story as a victim of abuse for participants in the Centre's online courses, now available in 25 countries worldwide.
Zollner acknowledged that part of this difference in approach is also found within Curia, as mentioned by Collins in her letter of resignation.
Survivors' groups and other critics have been skeptical from the outset of the commission's ability to effect change because it is an advisory panel with no authority to make rules.
The Pontifical Commission for the Protection of Minors said Marie Collins quit out of "frustration" at an alleged lack of co-operation from other Vatican offices, known as the Curia. "It is a reflection of how this whole abuse crisis in the church has been handled: with fine words in public and contrary actions behind closed doors".
Speaking to the National Catholic Register, Fr Zollner said that he understood Collins's frustration with the fact that not everybody was "on the same page" with regard to abuse prevention and best practices.
Collins noted she never had the opportunity to sit down with the pope to talk during her three years on the commission. Cardinal Sean O'Malley of Boston, who heads the commission, thanked her for her work and said the commission would look at her concerns at a meeting next month.
Ms Collins said she did not know if someone else would be sought to take her place on the Commission, although she suspected no-one else would be drafted in until the end of the year, when the terms of office of current members comes to an end.
Claudio Papale, an official at the Vatican's Congregation for the Doctrine of the Faith, resigned from the commission in May 2016. Collins wrote in her piece for the NCR.
The last straw came in January, she says, when a recommendation was refused and a request for cooperation denied.
In its own press release, the commission praised Collins for having "consistently and tirelessly championed for the voices of the victims-survivors to be heard, and for the healing of victims/survivors to be a priority of the church".
He said he was sure that in resigning, Collins's "intention is obviously trying to shock people into more resolute action".
Abuse victims support group One In Four said it was saddened Ms Collins had stepped down and that it appeared she had "no option" but to resign. She said she thought the problems had more to do with turf battles within the church than ideological or theological arguments, though she said that as an outsider it was hard to be sure.
She said the Pope had a "genuine wish" to solve the problem, but in later comments to a Catholic publication she criticised him for being too forgiving towards sexual abuse in the Church.
"If anybody can open up channels of communication, he can", she said.
"The voice of survivors at the moment is not represented by persons, but certainly by all of the members' experiences", he said, noting that all of the members, including O'Malley, have met with survivors on several occasions, "so it's not that the voice of survivors is not present anymore".
Collins, who was raped at age 13 by a hospital chaplain in Ireland, was the only active abuse survivor on the Vatican panel since British survivor, Peter Saunders, was cast a year ago for his outspoken criticism.
Collins, the only member of the panel who abstained from the vote to suspend Saunders, wrote at the time that it was unclear to some whether Saunders could work constructively and confidentially within the confines of the commission's mission.
It was seen as an attempt to address the bitter and long-standing scourge of child abuse which has dogged the Catholic Church.