In 28 matches dating back to 1994 the Wallaroos have never beaten the world champion Black Ferns, but get another chance in Wellington on Saturday.
Former England captain Yapp, who was appointed in December 2023, said she's seen steady improvement in her team on the back of more investment by Rugby Australia (RA).
"The aim was to try and bridge that gap and obviously New Zealand have had a head start in terms of being in a professional program for a lot longer, but the prep we've had coming into this has definitely allowed us to be to be better prepared," Yapp said from Wellington.
"The gap is obviously still there and we're just making sure that every time we play them, we're improving on our performance against them so we're excited to see how the girls step up on Saturday."
The Australian team are using the match to fine-tune their game ahead of the World Cup in England that gets underway in late August, with two home Tests against Wales before the tournament squad is named.
Waratahs lock Annabelle Codey, whose father is former Wallabies back-rower David Codey, gets a chance to stake her claim after being recalled to the Test arena for the first time in almost two years.
"Annabelle Codey has always been a player that's been on our radar, and I think to her own admission she didn't perform particularly well last year but she's gone away and worked really hard to make those changes and ... she's really stepped up," Yapp said.
Another face returning to the line-up is back-rower Piper Duck, who has battled various injuries in the past two years which in 2023 prevented her from taking to the field after being named Test skipper.
"Piper's had such tough luck around injury but she's an exceptional player when she's on the field and it's been great that she's managed to get back and return in time to put herself forward for the World Cup," the coach said.
Yapp will also blood another teenager with 17-year-old Waiaria Ellis named to make her Test debut on the wing.
Returning to her homeland after the World Cup Yapp said it was important that the women's program continued to be a priority, particularly with Australia hosting the next tournament in 2029.
"The last 12 to 18 months there's been a whirlwind of changes within the high performance program ... the absolute key thing now from RA's perspective is this momentum now, and the support and the funding that the players are receiving, has to continue post (2025) World Cup.
"It's really important that momentum continues with the home World Cup on the horizon."