"New Year, New Beginnings!!!" she said, accompanied by a smiling photo of herself.

Two months earlier, she had separated from her husband, Alexander Villaluna, and successfully applied to have an AVO in place against him.

She had since posted photos on her Facebook of flowers sent by "secret admirers" and birthday cards and gifts from her three children, who called her "the best mother there can be" and "an independent mother and woman".

However, on Wednesday night, Mr Villaluna allegedly attacked his ex-wife with a knife while she was on a first date with a new man at the Kangam BBQ restaurant in Westfield Hornsby.

Terrified diners screamed and ran as Mr Villaluna, 45, walked into the restaurant about 9.30pm, took a knife from the kitchen, allegedly stabbed Ms Pilapil in the chest and then allegedly stabbed her 53-year-old date, Keith Collins, who she had met on a dating website.

Mr Collins, a Irishman and father who lived in Terrigal on the Central Coast, died at the scene from stab wounds to his neck and throat.

Ms Pilapil was able to run away and hide in an upstairs shop, where she collapsed.

Witnesses said Mr Villaluna then calmly walked up and down the shopping centre's concourse, covered in blood and with the 20-centimetre knife in his hand.

After about 15 minutes, a female police officer with her Taser drawn apprehended Mr Villaluna, who had walked back inside the Korean BBQ restaurant and surrendered without incident.

A witness, Peter Dimbrowsky, said Mr Villaluna appeared "eerily calm" as he paced up and down.

"It's almost like it was an out-of-body experience for him," he said. "He probably sat down wondering what to do. He was eerily calm as though it didn't really matter."

Mr Villaluna, a Filipino man in Australia on a visa, was charged with murder and attempted murder on Thursday afternoon and did not apply for bail in Hornsby Local Court.

Ms Pilapil, who lists her job as the deputy director of nursing at Uniting Aged Care, was taken to Royal North Shore Hospital and was awaiting surgery for stab wounds to her chest, which punctured her sternum.

As recently as last week, she had posted a public photo on Facebook of flowers with the caption "another surprise... ‪#‎stalker‬ ‪#‎secretadmirer‬". It followed another secret bunch sent on her 39th birthday on March 8.

She had spent a week celebrating her birthday with her children and girlfriends and posting several messages hinting that she was determined to move on.

One inspirational quote she posted said: "I have already been through HELL. So give it your best shot. Not only will I SURVIVE, I will WIN."

In another post on February 12, she hinted at ongoing tensions.

"I was born on [sic] the year of the snake, a snake does not bite unless it is cornered and threatened. Just wait for it, I will give you the war you want!!!‪ #‎youhavebeenwarned‬."

In the weeks leading up to their separation in November, she was still posting photos with Mr Villaluna at a Robbie Williams music concert.

Mr Collins was remembered as a dedicated family man and "one in a million".

His adult daughter Aisling posted a photo of him online, saying: "I love you more than anything dad, I'll forever be your girl no matter what."

Michael Short, who works in the shopping centre, posted an image on Facebook of Mr Villaluna sitting on the edge of the fountain in the forecourt, holding a "massive hunting knife".

He said that he had just finished work when he saw hundreds of diners screaming and running, prompting him to grab a tyre lever from his car and to follow Mr Villaluna.

"[I] went back to the shop I was working in and there was another lady that he had stabbed in the shop upstairs that ran away," he posted online.

He said he spent about 45 minutes walking through the car park looking for a red car with Ms Pilapil's children in it.

"[She] had left her children in a car," he posted. "When I left they still had not found the car."

Mr Dimbrowsky said the manager of Kangham BBQ had screamed at people not to go near the attacker because he might have a bomb in his backpack.

Raphi Sakraphi, a waiter at next-door restaurant Infuzions, said he believed Mr Villaluna was calmly pacing up and down looking for Ms Pilapil as Mr Collins lay dead inside the restaurant.

Another witness, a young man, described the male victim dropping to the ground after being stabbed in the neck and stomach.

"[He was] panicking and stuff on the ground and he was yelling out, 'Help!' " he said. "He was laying there. I'm like, 'Mate, calm down, it'll be all good, just keep calm.'

"I was nearly in tears. Yeah, it was pretty messed up. As soon as I saw the blood coming out, I'm just like, 'Mate, I'm going to help you, just stay calm.' "

Detective Acting Superintendent Damian Henry said the incident was "certainly out of character for that area".

Investigators believe some diners filmed parts of the altercation on their mobile phones and they have asked for anyone with footage to contact Crime Stoppers on 1800 333 000.

With Ava Benny-Morrison and Megan Levy