The mother of two, 21, has regained consciousness and the family is hoping against hope she will leave hospital before Christmas.
In the same attack on October 11 in Omeath, Co Louth, Mackin, 25, murdered Garda Tony Golden.
He was helping Siobhán collect her belongings as she was about to leave Mackin having endured a year of violent, physical abuse.
Siobhán’s family has thanked the many people who have offered support and extended sympathy to the family of Garda Golden.
Her mother, Bronagh, said: “We would love to see her out of hospital in time for Christmas. She is loved by all her family and we are looking towards the future now.
“We think about the family of Garda Golden every day. His family has been in contact and his brother came to see Siobhán in hospital; that meant so much to us.”
Siobhán had surgery to remove a bullet that had lodged in her head after Mackin shot her. She has begun to speak but it is still “very early days” and the family does not know if her brain has been damaged.
Her aunt, Lorraine, said: “She is doing okay but we won’t know the full extent [of her injuries] until she really starts talking. At the moment she is not asking questions about anything, she is not curious in any way.”
Lorraine said doctors told the family that after a brain trauma, “the brain just shuts down. Siobhán doesn’t know what has happened to her at all.”
They believe she has no memory of the events and doctors “told her that she has been in an accident”.
Lorraine said her niece was shot in both arms.
“She must have had her arms up to protect herself. She was shot twice in her left arm and it ricocheted off one of her bones and there is some shrapnel embedded in her.”
Lorraine said the bullet to Siobhán’s forehead “never penetrated her brain”.
“The bullet hit off her skull and as a result of this injury she has lost her right eye. It is a miracle that she is not paralysed. She seems to be getting there but it is a long road ahead of her.”
Lorraine believes Siobhán was trying to leave Mackin for the last year and the beating on the Friday night was the final one she would endure.
“The only person who knows what happened in the house is Siobhán. The doctors said her memory might come back and then again it might not.”
Lorraine and Bronagh said their wish “is to have Siobhán well enough to leave hospital for Christmas Day, but we don’t think it will be this Christmas”.