The devoted Justin Bieber fan was hospitalised after a car accident in Heathcote, leaving her with broken ribs, a fractured spine and lacerations to internal organs.

Her plans to attend all Bieber's Australian concert dates were shattered so her friends started a Twitter campaign calling on Bieber to visit her hospital.

Instead, she was invited to a six-song acoustic set at a Docklands studio with 50 other "Beliebers" on Wednesday night.

"It was the best thing that I could ever imagine," Ms O'Neill told the Bendigo Advertiser on Thursday morning.

"I've been a fan since 2009, so almost five years now."

Ms O'Neill said the Bieber gig was the best experience of her life.

"I just can't believe it actually happened," she said.

"It was so crazy."

Ms O'Neill said the audience was not allowed to take photos during the performance but the gig was recorded on the online music video channel VEVO.

Bieber paid tribute to Ms O'Neill's devotion by expressing his love for his "Beilebers" before the end of the set.

Ms O'Neill's mum Jacinta also attended the gig.

"It was the biggest surprise of her life," she said.

"I think she's still in shock.

"She was just speechless.

"It was unbelievable.

"It was more than i could ever expect or imagine."

Jacinta said her daughter was in a private rehabilitation hospital and was on the mend.

"She's doing very well, really good," she said.

Tweets about the gig have been trending all over the world.

Bieber also tweeted after the gig.

‘‘That was fun and all for you Kate. Love u @BieberMelbourne . Stay strong," the pop star tweeted.

Meanwhile, just after 8pm Ms O'Neill tweeted : "BEST DAY OF MY LIFE I CANT BREATHE OMFG JUSTIN AND THE CREW ARE SO PERFECT".