The model mum paired the photobook-worthy moments with a caption filled with love.
"And she had the BEST day 🎉," Megan began.
"Blissfully oblivious to lockdowns, pandemics, riots and protests and completely absorbed and obsessed with unicorns, rainbows, ponies and Lego.
"I think she's onto something 😉 ROSIE • 4 🎈🦄💗🎉🌈🎁," she finished her post.
WATCH BELOW: Megan Gale makes her daughter a birthday cake. Story continues below.
On her Instagram story, Megan continued the celebrations by sharing a picture of Rosie posing with her toys with the caption, "Happy 4th Birthday Baby Girl."
Megan's mini-me is holding her balloons in the next slide, where she wrote, "It's a rainbow unicorn kinda day," with a cluster of party emojis.
In 2019, the model spoke to Australian Women's Weekly about her daughter's unique quirks and characteristics.
"She's like a cross between a wrecking ball and a koala," laughs Megan. "She's cheeky, fearless, determined, and just a firecracker."
However, she also revealed Rosie can be "insanely shy" around unfamiliar faces.
As for son River, the mum-of-two explained how he differs from his sister with his more "inquisitive" nature.
"He's a pretty quirky, pretty cool kid," Megan told the publication. "He feels very deeply. He's very emotional, and he speaks his emotions, which I've always taught him to do."
The doting mum has been open about the bittersweet arrival of her son, who was born during a time of tragedy.
Megan had been grieving the loss of Shaun's father, Tom, who had passed away from prostate cancer one month prior, while Megan's father, Alan, was in the final stages of lung cancer; he passed away 14 weeks after his grandson's birth.
"It definitely wasn't the experience I thought I'd be having with a newborn," she reflected.
When Rosie was born in 2017, the family was in a better place, and Megan could enjoy her birth without the immediate stinging pain of grief.
"River was kind of like a gift to get over the grief, whereas Rosie was just unadulterated joy. I had a new business and another child, but I found it a lot easier because I trusted myself a bit more. I didn't beat myself up about things. I just tapped into me," she shared.
This article originally appeared on our sister site, Now to Love.