The man was charged with murder after the woman's body was found in a Penrith unit on Monday afternoon.
Domestic violence journalist and campaigner Sherele Moody identified the woman as 28-year-old Dayna Isaac.
"Dayna was a mum to two daughters," Ms Moody said.
"She had known the man suspected of killing her for quite a while but their friendship only became a relationship in the past couple of months."
Her burned-out car was found in bushland nearby and is being examined.
Police were informed by a relative of the murdered woman.
The NSW Police tactical operations unit arrested a 32-year-old man at a house 5km away in Cranebrook on Tuesday morning.
"We are aware that there was a relationship between the two," Acting Superintendent Carlene Mahoney told reporters on Tuesday.
"It was a long relationship as a friendship and recently become more intimate over the last couple of months and that's as far as we're aware."
The man was taken to Penrith Police station and charged with murder.
Domestic violence campaigner Tarang Chawla, whose sister Nikita was murdered by her husband in 2015, expressed his dismay at the threat of violence still facing women.
"We are two weeks into 2023 and we now have two Australian women who have lost their lives to male violence," Mr Chawla posted on Facebook on Tuesday.
Mr Chawla and Ms Moody called for systemic and cultural change to make women more safe and stem the loss of life caused by domestic violence.
A national domestic violence offender register would be one way of doing so, according to Ms Moody, by enabling women to request the domestic violence history of would-be lovers.
"We have so much work to do," Mr Chawla said.
"And for Dayna and others, we damn well better start doing it."
A GoFundMe was set up Hayley Chandler, a friend of Ms Isaac, who said she was taken away too soon by "the hands of evil".
"Dayna was the life of the party and a friend to everyone. As you can understand this is a difficult time for her friends and family," the GoFundMe stated.
"We are asking for donations to help give Dayna the send off she truly deserves and to help with the costs of raising her children she's left behind."
The man is due to appear at Penrith Local Court on Wednesday.
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