Serinna, 15, was also named winner in the Youth category for the second year in a row. The Lismore High School student said it was a huge surprise to have been named Female Vocalist of the Year.
"I thought, 'I'm not going to win - I'm up against such professional women with such strong voices,'" she said.
"It's all so weird!"
She said she was pleased to have won for her song Thought of Love.
"I was proud of the song," Serinna said.
"I wrote the song in 10 minutes - It was like a diary for me."
"It's a very relatable song for teenage girls, I think."
She had written and produced Thought of Love with the studio time she had won after her success in the Young Songwriter's Awards.
She said working on the song was an experience unlike any other: "It felt really independent - like my own little project."
"Winning these competitions just gives you so many more opportunities - Now there's no excuse for me not to write more!"
Performing Thought of Love at the Dolphin Awards was "so nerve-wracking" for her, she said.
"It's funny because it's like a diary song, and it was my first time performing it, in the public sphere, telling everyone about my heartbreaks," the young woman said.
For winning at the Dolphin Awards, Serinna was "gratefully" awarded the "awesome" prizes of studio time, a mentorship, money towards her school's music department, and photo shoots.
So does Serinna ultimately want to earn her living as a musician?
"I do want to pursue it, but it is a hard industry," she said.
"I don't think I could have picked a harder career - I could probably go to clown school more easily than I could become a singer."
"But I just have to persevere - My dad always says you have to do what you love."
Serinna came to the region's attention when she wrote and posted a song to You Tube as a tribute to Rhys Holland, who died after falling through a sun shade. The video "Forever Young Rhys Holland" has had nearly 5000 views.