Mother-of-two allegedly murdered in apartment in Penrith, Sydney's west 

A mother-of-two found dead in her apartment in Sydney's west has been remembered as a 'beautiful and kind-hearted' person as a murder probe is launched.

Dayna Isaac, 28, was found dead inside her Colless St unit in Penrith, west Sydney, at about 4.15pm on Monday by a woman known to her who contacted police.

A 32-year-old man known to Ms Isaac is in police custody and is assisting detectives with inquiries.

Ms Isaac's best friend said she was the 'most beautiful, kind-hearted and selfless' person she had ever met.

'She lit up the room and was the life of the party,' the woman, who requested anonymity, told Daily Mail Australia.

'She was an amazing doting mother to two beautiful girls who absolutely adored her, and I am so so proud to call her not just my friend, but my sister.'

Another friend wrote to Facebook: 'RIP gorgeous girl, I'll miss you'. 

Ms Isaac's car was found burned out in bushland 13km away near Castlereagh.

Specialist forensic police are examining the home and what remains of the vehicle.

It's understood the 32-year-old man and Ms Isaac had been dating for a few months. 

'An investigation is underway after the body of a woman was found in a home in Sydney's west today,' a NSW Police spokeswoman said.

'About 4.15pm, a woman attended Penrith Police Station and notified officers that she had located the body of a woman – who was known to her – inside a unit on Colless St, Penrith. 

'Officers from Nepean Police Area Command attended the unit and found the body inside.

'Initial inquiries suggest another person had been at the unit prior to the arrival of the woman who reported the matter.'

Those living in the area have been rattled by the news about the death of their neighbour.

One local resident said she saw police cars lined up the street when she arrived home on Monday afternoon.

'I just heard the news, I was shocked,' she said.

'This area is pretty quiet, you don't hear about much happening around here. It tends to be more in Cranebrook.'

Another woman who lives in the same building as Ms Isaac said she woke up this morning to the property taped off and police officers scouring the site.

'It was quite scary, I was at work yesterday and found out over Facebook a woman had died in my street,' she said.

'When I came home late last night there was only one police officer there, but when I came out of the building this morning they were everywhere.'

Police are urging anyone who may have information that could assist detectives to come forward and contact Penrith Police station or Crime Stoppers.