Neve Cotgrave Hewitt died in the single-car collision in the early hours of Tuesday on the A442 near Trench Lock.
Neve's mum Penny Cotgrave, from Newport, said: "She was a diva. She was the most kind, caring, beautiful baby with attitude.
"She was sassy. I have just been watching my ring doorbell footage and in the last one she's belching and blowing me kisses. She was just crazy and adorable, she was just a beautiful soul.
"She was such a caring, loving little treasure. My life will never be complete without her."
Neve was a pupil at Burton Borough School in Newport and doted on her ponies, her mother said.
"She was just my amazing little princess, she loved her ponies – she had three ponies.
"The day before she died she said it was the happiest she had been in her whole life.
"I love her so much."
Neve had just entered Year 8 and had aspirations of going to university to pursue a career in Criminology.
"We had a birthday party for her last night [Thursday]," Penny added, "and everyone brought balloons and they let them go at the playing field at 8 o'clock - that's where all the girls used to hang out."
The balloon release on the playing field marked what would have been Neve's 13th birthday and saw a huge turnout from friends, teachers and the community who came to pay their respects.
Flowers, teddy bears and tributes have also been laid out for Neve, along with her signature pair of eyelashes that she wouldn't be without.
Penny said she was left lost for words by the outpouring of kind words and messages of support from her community, including from strangers.
"It's been amazing to be honest because I don't even know these people and it's just so kind.
"Everyone has been so kind, but I don't know what to say to them because 'thank you' just doesn't seem enough. For them to reach out, you don't understand how nice that is, and to see how everybody cared about my baby.
A fundraiser has been set up with the aim of raising £5,000 to go towards Neve's funeral and to give her the send-off she deserves.
Penny said it was amazing that someone she didn't know would put together a fundraiser to raise money for her little girl.
"I have no savings or anything. I don't want anything, I just want my baby to get the best send-off," she added.
Ben Morgan, acting principal of Burton Borough School, said a temporary memorial was in place for students to lay flowers for Neve, but the school team is looking at something more permanent.
However, the form this will take has yet to be decided on.
Special assemblies have been held at the school this week and parents have been told that students will receive all the help they need to deal with the tragedy.
Mr Morgan said: "We are allowing pupils to lay flowers and we have created a collage in reception of comments for Neve.
"What we are looking to do as a school is to name an area of the school after Neve and the students are looking to create artwork which will decorate that room.
"We have offered all our services to the family - counselling, and everything we possibly can to support them."
To make a donation to the fundraiser for Neve, visit justgiving.com/crowdfunding/Neve-memory.
A 36-year-old man also died in the crash on the A442. Two teenage boys were also injured.