Prosecutors said Danielle Watson, 24, of Rowhedge near Colchester, conned fundraisers in 2012 by claiming she needed to raise money for therapy.
The court heard she had already been given the all-clear by doctors.
Watson had denied the charges but changed her plea at a Basildon Crown Court hearing held in Southend.
In January 2012, the defendant announced she had stage four cervical cancer and had brought her wedding forward to April, so that it would take place before radiotherapy and chemotherapy made her hair fall out.
Following appearances in local media, she got free or discounted deals on haircuts, a wedding dress, a wedding reception at the Ivory Rooms in Billericay and, at fundraising events, she raised almost Â£10,000 towards "vitamin C treatment".
Marcus Croskell, prosecuting, told the court that when she had keyhole surgery for a common, treatable gynaecological problem in January 2012, she had already been given the 'all-clear' for cancer.
Fundraisers became suspicious when she failed to provide direct evidence of her illness or treatment and they called police after she used Facebook to announce she was pregnant in June 2012.
Mr Croskell said: "At no stage was she told by a medical professional that she had any form of cancer, let alone stage four cervical cancer, and she has never had treatment for it.
"Any such assertions are dishonest and false."
Ms Watson had denied six charges of fraud, but changed her plea to guilty on the first day of her trial, which was being held in Southend.
Det Con Rob Lewis of Essex Police said she acted in a "cold and calculated manner".
"She befriended and abused the trust of kind and generous people who wanted to help a person they thought was dying," he said.
"Everyone involved will be that bit more cautious and cynical the next time they are asked to make a donation."
Essex Police said some of the fundraisers had not handed over the money to her, but had been able to donate Â£6,563 to the Mercedes Curnow Foundation cervical cancer charity earlier this year.
Watson is due to be sentenced on 9 January.
A woman has admitted to fraudulently raising thousands of pounds ahead of her wedding by claiming she had terminal cancer.