McFarland said while Thursday's match wasn't the prettiest the team has ever played; the performance produced the required result.
"It was probably a little bit of a scrappy game when we look back at it," McFarland said.
"We countered efficiently and we were a lot more positive than we were in our previous games and we were a lot more effective in finishing off our opportunities. We did really well at the defensive end and Lilly controlled the back four and we were a lot tighter than the previous games."
"The players knew what we needed to win and that if we won we were pretty sure to go through. Getting that goal settled us down and allowed us to get more into our game and we started passing more quickly and efficiently."
With the team standing on the verge of achieving a long-held goal for women's football in New Zealand, McFarland says the spirit and determination which underlined the Junior Football Ferns' effort is something everyone can be proud of.
"I'm so pleased with the players. They took on the responsibility of keeping a clean sheet and taking on a battling approach to fight for a win and do whatever it took to produce a result. Those are some of the things you can't coach and it's up to players to stand up and that's really pleasing that they played to win."
The final whistle in Toronto sparked jubilant celebrations and McFarland says while they'll savour the moment, they are only part of the way to achieving their goal for the tournament.
"They're over the moon and that exhilaration of winning will last for a few hours.
"We set a goal of the semi-finals and that will keep the players' feet on the ground and help us keep focussed. I think the temptation is often there, now that we've made it through, to relax. We can't afford to do that. We'll enjoy tonight but tomorrow we'll be back to tuning in for the next game."
New Zealand 3-0 Costa Rica (half: 1-0)
NZL: Stephanie Skilton 24', Megan Lee 69', Tayla O'Brien 90+5'
CRC: -