It was at kindergarten that Katie Koullas realised her daughter Mia was not like most other kids.
"We noticed that she was having trouble connecting with some of her peers," Koullas told ABC television on Saturday.
"There were a few areas that were concerning me such as separation anxiety and sensory overload to things like heat."
Remarkably, it took doctors years to diagnose Mia with Aspergers' Syndrome -- a type of autism -- after a number of failed consults with psychologists and paediatricians.
As Australia marks World Autism Awareness Day, Koullas is making it her mission to help girls with autism find friends and thrive in what can be a challenging social environment.
Yellow Ladybugs, founded by Koullas, is a parent-run friendship group that brings together young girls with autism in a bid to "create a network of friends outside of school".
Events so far have included trips to the Melbourne museum and the National Gallery of Victoria, Koullas said, with the occasions often having the vibe of a birthday party including helium balloons, lolly bags, cupcakes and party-style games.
There are said to be more than 30 families on the waiting list for each event.
"It's been amazing," Koullas said.
"The events book out within 24 hours. It's all volunteer run and great to see the girls come together in the Yellow Ladybugs T-shirts and meet girls who are sharing their journey.
"Yellow Ladybugs has been great to start that awareness and acceptance, but what we're trying now to do is to shine a positive light on girls and ... get more awareness out in Australia about the fact that girls are getting misdiagnosed."
She said support for girls with autism was especially important as the signs could be hard to spot.
Officially, there are many more boys than girls diagnosed as autistic, but experts consider that statistic misleading.
"They may hold their anxiety together at home and they may feel that they need to relax or unwind or sometimes they even melt down because it's been so hard to hold it in. So that's how they fly under the radar," Koullas said.
"Another thing could be their special interests aren't as different as say, for example, boys. It might be a really strong passion in fashion or animals, so it's not easily picked up."
Find out more about the signs of autism here.
To help mark World Autism Awareness Day, global landmarks like the Empire State Building, Arc de Triomphe, Egypt's pyramids and the Sydney Opera House are being turned blue.