In Cromwell they are missing five players from that squad - captain Stacey Michelsen, Sam Charlton, Liz Thompson, Amy Robinson and the recently-retired Pippa Hayward - and were defeated by Japan and Australia on consecutive days to start the tournament.
However, they picked their moment to shine.
Trailing 3-1 in the must-win play-off, a late Sam Harrison goal and Merry's penalty stroke from the final play pushed the game beyond fulltime.
Merry's effort came on the back of three successive penalty corners.
The world No 4 Black Sticks' opening goal came from Shiloh Gloyn. Mai Toriyama scored twice and Yuri Nagai once for 12th-ranked Japan.
"I had three consecutive heart attacks and a penalty stroke to sit through," O'Hanlon quipped.
She was prepared to replace fellow custodian Sally Rutherford.
"The more confident I appear, the more confident I feel, and that's a positive spiral to get into. I find it helps if I come on as if we've already won.
"Once the game starts you get invested in it and almost forget you're on the bench.
"Being 3-1 down at three-quarter time it seemed an unlikely comeback, but as we crept closer to the end of the quarter I thought 'we might be on here'.
O'Hanlon expected the team to engage in some "serious talk" when they got home if they are to repeat their Commonwealth Games success at this tournament.
"We need to tighten up at the back," she said.
"It's nice to know we can beat Aussie. I'll be ready, and hopefully they'll be sweating a bit about that."
