Lauren O’Neill visited Donegal with a number of friends and had been to a number of nightspots in the town.
Tragic Lauren died when she was blasted to death at a house in Bellaghy.
Her 21-year-old sister, a mother of two young children, was seriously injured and remains in a critical condition at Belfast’s Royal Victoria Hospital.
She managed to make it to a neighbour’s house to raise the alarm.
A Belfast Trust spokesperson confirmed that she had undergone surgery on Saturday afternoon.
A 26-year-old man is still being questioned by police on suspicion of murder.
A man and woman, both aged 28, arrested on suspicion of assisting an offender were released, without charge, on Saturday evening.
They were all arrested in the Toome area within an hour on the shooting.
Parish priest Fr Andy Dolan said the feeling in the area is one of “shock and horror.”
He said that the siblings were always together – if you “saw one you saw the other.”