Kate Keenan had just turned 25 when she suffered fatal injuries in the horror crash in Carnalogue, Ireland at 1.50am on Monday.
Kate’s sister Rachel penned an emotional tribute on Facebook, writing: “How am I going to do life without my beautiful little sister?
“You were the strong one - not me. I never wanted you to leave me.”
Her cousin Rebecca said she was “devastated”, writing: “My beautiful cousin. I am absolutely heartbroken.”
Her death came hours after father-of-five Jimmy Rowe was killed in a single-vehicle accident after his car skidded on a flooded road during the storm.
The builder, in his 40s, was pronounced dead at the scene after the car he was driving veered off the highway in Claremorris around 6.15pm on Sunday after dropping off his daughter.
His devastated brother Albie Rowe announced his death on Facebook, writing: “Folks, with a heavy heart I bring you the heartbreaking news that our baby brother Jimmy Rowe has lost his life on the roads.
“Give your loved ones a hug, you never know when it’s the last. love you forever, Jimmy.”
Councillor Killilea, for Galway County Council, said: “I believe Jimmy was dropping his daughter to the north western region and he was on way home to Co Galway when he tragically lost his life.
“He was a nice quiet man and worked in Tuam. He worked in the building trade and been living in the area for a few years. My sympathies go out to his family in Longford, and to his partner and all his friends here.”
A third victim, a man in his 60s, was killed after his van collided with a fallen tree and a vehicle at 9.45pm on Sunday along Broad Road in Limavady, Co Derry.
In Scotland, an 84-year-old man died after the car he was a front seat passenger in crashed into a fallen tree.
It comes as Storm Isha subsides to make way for Storm Jocelyn expected to thrash the UK with more wind and rain tonight and into Wednesday.
Gusts of 80mph could be experienced in exposed areas, with 40-50mm of rain possible over higher ground, the forecaster said.
Gardaí are appealing to anyone who may have witnessed the collision that killed Kate Kenan to contact them.
Anyone with any information is asked to contact Ardee Garda Station on 041 685 3222, the Garda Confidential Line on 1800 666 111 or any garda station.