In a last-ditch effort to remain in Australia, the Sydney karate instructor will meet officials from the Department of Immigration on Monday.

Hers is a complicated story but one that is becoming increasingly common as people travel the world with greater ease and form relationships with partners of a different nationality.

Ms Henriquez was born in Venezuela but married a US citizen. The couple had been living in the US when a job opportunity brought them to Australia in 2008.

Three years ago the couple separated. Ms Henriquez wished to return to the US where her extended family live but her estranged husband wanted to stay in Australia.

"He said sorry I love it here and I want to stay forever. I said, 'What about me? What about the kids?'," she said.

She remained in Sydney, opening a karate school on Sydney's north shore and caring for the children, Sophia, 6, Tomas, 7, Mateo, 9, and Diego, 11.

Ms Henriquez's visa expired on Saturday but she says her estranged husband applied for bridging visas for the children and was successful.

"It's very unfair," she said. "It is a mistake. My children are at risk of losing their mother."

Ms Henriquez believes her only option is to apply for a bridging visa E which will allow her to stay in Australia temporarily while she makes arrangements to leave. As she no longer has residence status in the US, she will most likely have to return to Venezuela, leaving the children behind.

"I am so worried about being separated from my babies," she said. "I think about it every second of the day. I can't sleep at night. I won't rest until I have this cleared up."

Her solicitor, John Haddad of the Macarthur Law Group, says his client faces every parent's worst nightmare.

"It's a very unfortunate situation and she's quite distressed about it," he said.

Ms Henriquez's friends have started an online fundraiser to support her while the matter is resolved.

The Department of Immigration and Ms Henriquez's estranged spouse have been contacted for comment.