A man (40s) has been arrested in relation to the collision which left one woman dead and two others seriously injured
The physiotherapist was standing with several family members by the roadside in a Cork village when the tragedy occurred shortly after 1am.
Gardaí have arrested the driver, a man in his 40s, who was taken to Bandon Garda Station for questioning.
He is expected to be released without charge with a file now to be prepared for the Director of Public Prosecutions (DPP).
Ms Twomey, who was from Ballyvourney in Cork, but had been living in Dublin, had returned home to attend the funeral of a relative.
The west Cork Gaeltacht village of Ballingeary was in shock today after the tragedy, which left Ms Twomey dead and two others seriously injured.
The tragedy occurred at Dromanallig off Ballingeary's Main Street around 1.10am.
Ms Twomey was standing with several family members when the tragedy occurred.
It is understood that she was among two groups of mourners, who had attended separate local funerals, and had met on the main street as they were heading home.
The group of around five or six people stopped to chat and sympathise with each other.
As they stood by the roadside, a vehicle approached and ploughed into the group.
Ms Twomey suffered fatal injuries and was pronounced dead at the scene before she could be rushed to Cork University Hospital (CUH).
Two other women suffered serious injuries.
They were transferred to CUH where they remain in a serious but stable condition.
While their injuries are described as serious, they are not understood to be life threatening.
Ballingeary Main Street was closed to facilitate the work of Garda Forensic Collision investigators who will conduct a full technical examination at the scene.
Local diversions were in place and motorists have been urged to avoid Main Street.
Gardaí are now appealing for any witnesses to this collision to come forward.
Anyone with any information is asked to contact Macroom Garda Station on (026) 20590, the Garda Confidential Line on 1800 666 111, or any Garda Station.
Weather conditions will be examined as part of the investigation into the tragedy with parts of Cork witnessing icy conditions and temperatures which plunged below zero.
However, icy road conditions are not now believed to have been the primary contributing factor in the tragedy.
Councillor Eileen Lynch said the area was in deep shock after the tragedy.
"This is a close-knit community and it has come as a massive shock. These are terrible tragedies but it is particularly tragic when it occurs so close to Christmas."
"It makes it very, very difficult for the families involved and my thoughts and prayers go out to them."