Sarah Johnson was one of 21 women heading to Liverpool when their minibus was hit by a lorry on the M62.
Her friend Bethany Jones, 18, was killed while Ms Johnson and several others were badly hurt.
Minibus driver James Johnson was jailed for more than six years for causing Bethany's death, in April 2013.
Ms Johnson, who broke her shoulder, back and pelvis, said the help she received from a charity while in hospital led her to want to support others.
Speaking publicly for the first time about the crash, Ms Johnson described how everyone was "excited and giddy" for the hen party.
"To me the impact was just a massive explosion," she said.  "I thought the bus had blown up.
"I remember the bus dropping on its side. The next thing, I woke up on the roadside so I'd actually come out of the window."
Ms Johnson was taken to Leeds General Infirmary where she, along with Bethany's sister Amy Firth, underwent major surgery and spent time in intensive care.
Whilst she was there she got support from charity Day One, which helps victims of major trauma.
She said: "It's absolutely fantastic.
"It supports people by giving benefit advice, legal advice and peer support such as me and Amy, who have been in similar situations and who are now helping other people who've suffered from major trauma."
Ms Johnson said the crash had made her realise how lucky she had been.
"Beth can't complain, she's not here," she added.  "We just have to be grateful for what we've got."
A woman who was seriously hurt in a fatal hen party motorway crash is now helping other major trauma victims rebuild their lives.