During her illness and after her death, the Candlelighters charity has supported Diane Crann, 53, and Ella's brother Harry, 21.
So the family organised Ellafest, which brought live entertainment, a DJ, raffle and many memories of the Bruntcliffe Academy student to the Gomersal Park Hotel on March 23.
Her birthday would have been on Thursday, March 21.
Speaking today, Miss Crann thanked everyone who supported the event, saying that more than £5,000 has been raised so far.
Paying tribute to her daughter, she said: "I can't be more proud of her - she was so strong and determined. She still thought about other people and put other people before herself."
The teenager also loved music - once meeting Ed Sheeran in Paris after her diagnosis - and the glitter-filled festival reflected that interest.
Rock sing-a-long band Sillie Billie provided entertainment for the roughly 160 people who turned out.
DJ Cookie also played tunes for the disco, and raffle prizes included theatre tickets, a massage and more.
"Everyone dressed up and just had a really good time, and supported us really well," said Miss Crann.
"We was just overwhelmed by the generosity of everyone.
"Harry and myself would just like to thank everyone that helped."
Despite undergoing intensive chemotherapy and the Clarendon Wing of Leeds General Infirmary becoming a "second home", Ella's family said that she remained positive during treatment and even planned her own funeral.
Candlelighters visited Ella at home when she was ill and has maintained its support of the family over the last four years.
Miss Crann said that the family has raised funds for it ever since with various activities, and she has become a volunteer.
"It's just nice to be able to give something back," she said.
"I will never be able to thank them enough, it means so much forever."