Ms Ward's body was found by police at her home in Melrose Street in south Belfast on October 1st.
Stormont 's First Minister has said police have questions to answer regarding their dealings with Mary Ward prior to her murder.
A 26-year-old man was arrested in Dublin on Wednesday on suspicion of her murder. Ms Ward, 22, had previously reported being the victim of an assault on September 4th and a suspect was arrested and questioned in relation to that incident.READ MORE: Man arrested in Dublin on suspicion of murder of 22-year-old Belfast mum
Ms O'Neill was asked about the case as she spoke to reporters in Belfast on Wednesday and said: "I am very concerned, I think we all should be very concerned, the fact that this apparently was reported before she tragically lost her life. This is catastrophic that this is happening again in our society so collectively we know that we have a lot of work to do to end violence against women and girls.
"My thoughts absolutely are with Mary's family and her friends at this really difficult time. But of course this does emphasise why this needs a whole systems approach and a whole community approach to tackling the scourge of violence against women and girls, it is simply unacceptable.
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