Banyana Banyana surprised everyone but themselves when they beat Italy 3-2 on Wednesday to reach the knockout stages of the tournament and set up the clash against the 2019 World Cup finalists at Sydney Football Stadium.
"We've been underestimated so many times before," Ellis told reporters.
"I think this group has shown that nothing can stand in their way, this group has shown when the chips are down that they can stand up. We know who we are playing, but they don't know who they are playing.
"Because this group when the chips are down, they've just gotten better and better. And all I can say is that there's going to be a match tomorrow."
Striker Jermaine Seoposenwe said the criticism the team received after leading their opening match before losing to Sweden and then giving up a two-goal advantage to draw with Argentina, had helped motivate her.
"No one gave us a chance to get out of the group, we are African champions and people still didn't give us a chance," she said.
"So I think for me, I just took it personally. And that's why I play the way I play. I want to show that we are a team to be reckoned with and that we can compete at the highest level."
The Dutch beat South Africa 5-1 in a friendly last year but Ellis said not much should be read into that result.
"We are a team that know what our strengths and weaknesses are ... we know what we want to do. I think the opponent knows what we want to do and sometimes they can't stop it," she said.
"We've got to bring our 'A' game and we've got to be at the absolute best, because the Dutch have shown during the tournament that they're a top side."
