The Corrections Department cited similar reasons for refusing to divulge if Xiao was still under its management.
However, New Zealand First Leader and Northland MP Rt Hon Winston Peters had been told Xiao would be deported on Wednesday.
He said it was a "travesty of justice" that the Chinese national would be going home without completing home detention.
"New Zealand is saying to the world: you can behave recklessly here, cause the death of a New Zealander and go home.
"That's no penalty."
Rhys Middleton's mother, Judy Richards had also been called by victim support person and informed Xiao was currently in a detention centre in Manukau - pending a likely deportation on Wednesday.
"It's not very fair," she said. "It's a slap on the hand with a wet bus ticket."
Richards said it was impossible to just move on following the death of her son.
"You just cope as much as you can, nothing can change the fact that he's gone," she said. "It's his birthday on September 14 - it's going to be a tough one."
Richards wanted a change in the law to ensure those sentenced to home detention be forced to serve their time before they were deported.
"That's what we'd like," she said. "If we can pave the way for people to have a less stressful time, then that will help in some way.
"It's very important to us, a life has been wasted needlessly," she said. "Not only Rhys, it's been countless others and it needs to stop."
In the High Court judgement released last week, Justice Jillian Mallon said the sentencing decision should have looked at whether jail time or home detention was more appropriate - regardless of the immigration consequences.
She added because the woman was remorseful and it was her inexperience, rather than other "aggravating features" such as drugs or alcohol, behind the tragedy, home detention was more appropriate.
Despite numerous queries from the Herald INZ denied a date had been set for Xiao's deportation.
Jehle said "no decision has yet been made, but all the circumstances will be taken into account before that happens".
But she said it was the "normal process" to deport criminal offenders who have been served a deportation order before they serve any period of home detention.
"If a criminal offender is not in prison, but is in the community, INZ can deport that person if they fall within the criteria for deportation set out in the Immigration Act 2009."
Under the act a person on a temporary entry class visa who has committed an offence for which the court has the power to impose imprisonment for a term of three months or more is liable for deportation.
Owner and principal at Ryken & Associates David Ryken said there was nothing to prevent INZ from deporting a person who'd committed an offence.
"It's up to INZ to allow them to complete a sentence, or bring it forward and deport them," he said. "There's no assumption they can sit out their home detention at all.
He said deportation could also happen very quickly.
"When I'm wearing my hat as a New Zealand citizen, I think she should serve her time," he said. "But the practical reality is there's nothing to stop it."
Attempts to contact Xiao through her lawyer have been unsuccessful.
