The heartbroken friends and family of murdered Sydney dentist Preethi Reddy say she was the happiest she’d ever been just before her “unthinkable” death.

“Words cannot capture the pain we are feeling,” her sister Nithya said in a statement on behalf of Dr Reddy’s grieving family on Thursday.

“Preethi was a bright light, loveable, kind, and protective of all whom were lucky enough to have been loved and cared for by her.

“Prior to this unthinkable event, she had been the happiest I’d ever seen her – she was living her best life.”

Dr Reddy’s parents and current boyfriend were enduring the toughest time of their lives, Nithya Reddy said.

“We ask that everyone keep that in mind that we are grieving and we need space to do that,” her statement, released by NSW Police, said.

“Let the police do what they need to do to solve this horrific tragedy. Our family will never be the same without Preethi our lives.

“Please let her beautiful soul rest in peace.”

Dr Reddy’s body was found in a suitcase in the boot of her VW Golf in a lane in Sydney’s east about 9.30pm on Tuesday, almost three days after she was last seen.

Police said she had been stabbed “numerous times”.

Her former boyfriend, Tamworth dentist Harshwardhan Narde, 34, had hours earlier taken his own life in a fiery car crash on the New England Highway. Local police are investigating the collision, and are treating it as “a deliberate act”.

Dr Narde died in this crash on the New England Highway. Photo: ABC

Investigators believe they know who killed Dr Reddy but are pleading for more information about her whereabouts before her death.

They believe she reconnected with Dr Narde in Sydney but are still trying to understand exactly what happened.

He was reportedly seen on CCTV getting into Dr Reddy’s car on Sunday outside the Swissotel on Market Street in Sydney’s CBD.

“It’s very important for us because, right now, we are working for Preethi and we are working for Preethi’s family as well,” Detective Superintendent Gavin Dengate said on Wednesday.

The gruesome discovery of Dr Reddy’s body on Tuesday came just hours after police issued a public appeal to find the 32-year-old from Penrith.

She was reported missing on Sunday after she failed to return home following a weekend dental convention at St Leonards.

She was captured on CCTV inside a Sydney McDonald’s about 2.15am on Sunday and appeared to leave alone.

She last spoke with her family about 11am that day, saying she planned to head home after having a late breakfast.

Dr Reddy worked at Glenbrook Dental Surgery in the lower Blue Mountains.

Her colleagues posted a tribute on Facebook on Wednesday, saying staff at the clinic were “in mourning” after hearing the news of her death.

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-with AAP