When police posted a Facebook appeal searching for a woman wanted over the theft of an 86-year-old woman's handbag, they did not expect the suspect herself – and her sister – to start arguing with them in the comments.

Kellie Beasley, 40, is wanted for nine different offences across the UK, including fraud and the theft of an elderly lady's handbag. Wandsworth Police wanted help from members of the public as they said she is an "accomplished fraudster" with no intention of handing herself in.

The post said: "Kellie pops up everywhere, from London to Bristol to Grantham to Staffordshire. She particularly likes to approach businesses claiming to be from their head office, allowing her to make off with their takings in cash.

"We'd like to speak to Kellie about this matter, and when officers last spoke to her on the phone, she told them she was in Cardiff and would hand herself in. However our colleagues from South Wales Police Cardiff have not heard from her since, and we suspect she might have been lying to us..."

However, it took just three hours from the post being published on Tuesday afternoon (20 February) for Beasley to get involved and begin arguing with police. She appeared to confess to fraud offences but deny stealing from an elderly woman.

She wrote: "They're lying I will prove it yes fraud not old women all my people no [know] I wouldn't do that f*****g pig liars and the police will be apologising."

Wandsworth Police replied, urging Beasley that the quickest way to deal with the allegations against her would be to hand herself in at her nearest police station, or tell them where she is so they can travel to her. "It will get the matter sorted much quicker than arguing with us online," they wrote.

But she continued, replying: "f*****g tell the truth then you f*****g no I ain't robbed no old lady that's why your replying." She also threatened to sue the force for lying.

Beasley also joked that police should have used a better photo of her, and called another Facebook user a snitch, writing: "why u felt the need to come on here with ya snitching bullshit I don't know??? You don't no me or my family so stop talking bollocks........"

Beasley's sister, Nina Louise, also commented on the thread, taking offence at accusations of other offences from users and stating she would also make a complaint. She wrote: "So the further comments on here accusing her of all sorts are acceptable are They??? Threats to the family?? Part of a pedo ring?? What really is going on there as I stated I am writing a complaint." She added: "Terrible terrible service and a traumatic effect on the family."

Upon being accused of leading a witch hunt by releasing details of accusations against Beasley without her being arrested, Wandsworth Police revealed that she had been convicted of 18 frauds in May last year - "some of them very high value". She is currently serving a suspended sentence of eight months' imprisonment which was suspended for two years for those offences.

They added: "We are not leading a witch hunt, we are trying to track down a woman who is wanted as a suspect for multiple offences across the UK. We have sufficient cause to believe that she has committed these offences, or she would not currently be wanted. As soon as she is found, her image can be removed from social media."

Many people pointed out that Beasley had brought attention to the post herself by commenting on it - and some called it "comedy gold". The post has been shared 1,600 times.

The Metropolitan Police said today "enquiries are ongoing to establish whether the person who has made contact with officers is Kellie Beasley".