Athletes must have the required identification and meet certain testosterone levels.
Monaghan said she felt the pressure at the national tournament.
"There was an added pressure there. Being who I am, it made it a little bit more difficult, because there were a few voiced opinions there not believing that I should be there."
She said making history as the first transgender woman to qualify for the world championships was starting to sink in, but she did not look back on the national tournament with great fondness.
"It's a little tarnished with a few of the comments that were made, but it's still sinking in.
"I don't think I've quite realised how big and significant this is.
"I guess when I get over there, it will be more of a realisation that this is a dream come true. You know, this has been a dream of mine since I was seven years old to play on the world stage. So it's huge for me."
Monaghan was a national-ranked player in the men's field up until about 2018, when she gave up the sport.
In the past few years she has transitioned to female, saying she felt "different" from a young age.
This year she decided to return to darts, but ran into issues.
The Clubs New Zealand Darts Association barred her from competing in the West Coast Championships in June because it did not have a transgender policy, before changing its mind and allowing her to compete.
At the NZ Open two weeks ago, Monaghan was confronted with a number of hecklers while competing, but held her nerve to win the title.
She said having success as a woman was "huge".
"I think being truthful to yourself is the biggest thing. I am now, and I'm very happy with where I am in life.
"It's taken me a good few years for this to settle down, and accept who I am, and adjust to it as well.
"It's a massive mental game. You go through a lot of waifs and strays, you know, you have a lot of thoughts, and there's a lot of down moments and dark moments in your life.
"But if you can stay positive and true to yourself, you'll always come through on the other side."
Monaghan is now trying to fundraise, through auctions and a Givealittle page to get to the World Darts Championship in January, and the World Masters in the Netherlands in December.
She plans to train two to three hours a day until closer to the tournament, and will play some of New Zealand's top players to prepare.
"I have some top end players that have offered to kind of give me practice games and push me harder, to try and focus me on different things and improve my game hopefully to a level that can bring back the World Championship.
"I mean, there's no point in going if you're not going to try and win it, is there?"
