The requiem mass, at Christ the Redeemer Church in the Lagmore area of the city, took place as detectives continued to hunt for the killer.
Parish priest Fr Martin Graham said: "Whoever did this to Jennifer has turned her death, which was cold-hearted and callous already, into something that was wicked and obscene.
"A family home has been destroyed as her family's hearts have been torn apart."
Friends and family dressed in bright clothing packed into the church, not far the scene of the crime, for the hour-long service.
Ms Dornan, who leaves three children - Martin, Jayden and Abi, all aged under nine - was described as fun-loving and outgoing.
Fr Graham said: "Jennifer was a vibrant human being with a love of life and a joy and energy that attracted many friends. She enjoyed life so much and she was the life and soul of any party.
"Jennifer knew what she meant to a great many people and she enjoyed company. She was quick and razor sharp in mind and in tongue.
"She gave everyone plenty to laugh and smile about and she never had to try hard.
"Her nature, her personality, was one that even with her own troubles and worries she could still smile and help others to do the same.
"This world is the poorer now that Jennifer has left it, and with her buoyant personality it will also be so much quieter."
Mourners were asked not to send flowers, instead donations are invited to a GoFundMe page which has so far raised almost £16,000. The GoFundMe page was set up by a friend devastated at the loss.
On Thursday detectives investigating Ms Dornan's murder released a photo of a knife similar to one which they believe was used to attack her.
Ms Dornan - who had only celebrated her 30th birthday in May - died at her home on Sunday morning. Emergency services were called to Hazel View in Lagmore, just before 5am, but they found Ms Dornan dead at the scene.
On Monday evening the PSNI launched a murder investigation following results of a post mortem.
Police have now issued a photograph of knife they believe is similar to the one used to stab Ms Dornan before her home was set on fire.
The officer leading the investigation, Detective Superintendent Kevin Geddes from Serious Crime Branch, said: "I can confirm that Jennifer was stabbed during the attack early on Sunday morning.
"We are appealing to anyone who has come across a knife like this since Sunday to contact us. We are grateful to the community for the enormous amount of assistance they have provided in the past few days and would ask for their continued support."
The PSNI said they are 'following a definite line of enquiry'.
A 39-year-old man remains in custody being questioned about withholding information. Other enquiries are continuing.
Detective Geddes added:"We are particularly interested in the movements and whereabouts of a man seen leaving Jennifer’s home at 4.20am on Sunday. We believe he walked from Hazel View, through Lagmore to Poleglass. We believe he was wearing a grey tee-shirt or sweat top and a light coloured bomber jacket.
"At some stage, we believe he got rid of the grey top and light coloured jacket and obtained a red and gold sports jersey.
"We are appealing to anyone who lives on the route between Hazel View and Poleglass and who has knowledge of any of these items of clothing or the knife to contact us."
Father's plea for help in finding killer
At a vigil on Monday night Ms Dornan's grief-stricken father, Stephen, made an emotional plea for help in finding her killer.
Mr Dornan appealed to the local community to bring any information they had to the police, so that his daughter's killer could be brought to justice.
"Whatever you've seen - how little, how big, how small, come forward," he said.
"This animal killed an innocent, defenceless woman in cold blood.
"However little you know, come forward, and he'll be off the streets tomorrow - before he does this to somebody else."
Sinn Fein MLA Jennifer McCann said the community had been left stunned by the murder.
She said: "This news has sent shock waves through the local community who have rallied round her family.
"I am urging anyone in the community with information which may assist the police inquiry into Jennifer's death to come forward right away.
"This is a time for calm heads and the community needs to support the family and help the police get on with their job of finding Jennifer's killer."
Anyone with information is asked to contact detectives on the non-emergency number 101 or use the independent charity Crimestoppers number 0800 555 111 if you don’t want to provide your details.