The women's sevens side regained their world championship this season, after securing the silver medal at the Rio Olympics.
Their programme received $1.1 million from High Performance Sport New Zealand's December 2016 funding round and individual performance enhancement grants of $30,000 per annum.
They are guaranteed further investment until the Tokyo Olympics.
"The reality is that the fifteens programme doesn't sustain a full-time athlete at this stage, but the game is growing quickly," Tew said.
"The publicity this team has created in the last 48-72 hours is something we have never had before.
"The country has never really stopped to watch a [women's] final like it did on Sunday.
"Certainly we've never had the whole front cover of your newspaper devoted to women's sport before, let alone women's rugby. But we've got to do it [instil professionalism] in a sustainable and realistic way."
The players accepted the balance sheet would struggle to sustain any major investment, for the time being.
Captain and hooker Fiao'o Faamausili will resume her job as a police detective next week.
"I breathe professionalism in my job and in my rugby. I always wanted to represent my country in the sport I love, and always wanted to serve and protect my country as a police officer."
Halfback Kendra Cocksedge works as a women's development officer for NZR in the Crusaders region.
"There's been a lot of talk around that [turning professional] but until we get more games a year, it's probably not going to happen."
New Zealand's 41-32 victory over England in the final at Belfast also brought suggestions, some possibly tongue-in-cheek, to change the team name to the All Black Ferns in line with the decision to link the All Blacks moniker to the Maori and men's sevens teams.
Tew doubted the current team name would evolve.
"When we name teams, we talk to the athletes and I know this group is proud of the Black Ferns name.
"It's got a lot of mana now and they've won five World Cups, so any change would have to be seriously considered and athlete-driven, as much as anything else."