"The probability of contagion in NSW - given what's happening in Victoria - is extremely high," she told reporters.
"The probability that we need to be tougher on those border restrictions is extremely high. The government is considering what further action we take to make sure the bubble of these border communities is maintained."
NSW on Wednesday recorded eight new COVID-19 cases including seven in hotel quarantine and a woman in her 30s from southwest Sydney. The woman's case remains under investigation.
A teenager on holiday in Merimbula has also tested positive for the virus.
Victoria recorded 134 new coronavirus infections on Wednesday morning as Melburnians prepared for a looming six-week lockdown.
Premier Daniel Andrews on Wednesday said 75 infections had been recorded in the nine Melbourne public housing towers that are currently under total lockdown.
"We are all working as hard as we can, doing the very best that we can, and we know that we're asking a lot of Victorians and we know, of course, that we didn't want to be in the position that we are in," Mr Andrews told reporters.
At midnight on Wednesday, metropolitan Melbourne and Mitchell Shire will revert to stage three coronavirus restrictions, in a bid by the state government to regain control over a growing epidemic.
"If we all work together over these next six weeks, as painful and frustrating and difficult as that will be, we will be able to get to the other side of this stay-at-home period," Mr Andrews said.
"We'll all be working incredibly hard, incredibly hard, day and night, to deliver that outcome. Of course, every Victorian has to join us in that effort. I'm confident they will."
Mr Andrews also apologised on Wednesday for the hardship many Victorian families would endure over the next six weeks.
"I apologise for the inconvenience, the great challenge that many, many Victorian families are going to have to experience over these next six weeks. It's not where we wanted to be," he said.
"But we can't go back. We can't change those things that have got us to this point. We can only respond appropriately and that involves everyone following the rules because they are rules that are there for everyone."
However, he refused to shy away from comments he made on Tuesday, where he criticised some Victorians for becoming complacent about the COVID-19 threat.
"I think that's an accurate description of the way some people are behaving," he said on Wednesday.
"Part of my job is to be as frank and as clear as I possibly can and that's exactly what I've done."
Authorities hoped to complete testing at the nine public housing towers by the end of Wednesday, Mr Andrews said.
Some 3000 people are living under a total lockdown inside the public housing towers.
"We are very confident that we will be able to complete testing today," Mr Andrews said.
"I again say to every single resident in those towers you will be under these restrictions for not a moment longer than you need to be, for your safety, for your health and welfare, as well as for public health."
Residents in affected public housing towers who need access to support and assistance should call the Housing Call Centre on 1800 961 054. If you need a translator, first call 131 450. Both services are 24/7. More information can be found here.
People in Australia must stay at least 1.5 metres away from others. Check your state’s restrictions on gathering limits.
If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080.
News and information is available in 63 languages at sbs.com.au/coronavirus