Scenes of jubilant Green supporters hearing the news when it was announced at North Lanarkshire's count have been shared far and wide.
"We were really taken aback!" she said. "We only found out when the returning officer read it out, which is why the celebration was quite as raucous as it was!
She heard the result with a combination of "sheer joy and disbelief".
"I'd convinced myself all day on Saturday that it wasn't meant to be," she said.
"We put game faces on and went to the stage expecting bad news, so it was complete joy when it was read out!"
For Gillian it was a bitter-sweet moment as her mum, Audrey - a primary music teacher in Falkirk - passed away in December, aged just 60.
Then, just six weeks ago, she also lost her grandpa.
"It's awful they're not here to see this because they knew this was happening - they'd been there since I was selected," she said.
"But I've really appreciated all the messages I've had from people who knew my mum to say how proud she would have been and how much she'd be cheering me on.
"My dad, sister and brother and my other half have been supporting me and I couldn't have done any of this since December without them."
Despite her loss, Gillian focused on the campaign and enjoyed it, particularly the online hustings were well attended and good-natured.
"It was odd not being able to chap doors and speak to people so I'm very much looking forward to hearing from constituents on local issues."
A graduate in marine biotechnology and biodiversity, Gillian has worked as a staff member for the Green MSP's for several years, so she's well aware of how the parliament works - and she knows what her priorities are.
Having grown up near Ineos - she only recently moved to Laurieston - Gillian knows how important the petro-chemical industry and the jobs it provides are to the area.
But she also knows the downside.
"Within the boundaries of Grangemouth we have some of Scotland's biggest polluters and I think a lot of the public - and certainly the younger generation - realise that a lot of these industries need to transition and do it very quickly if we're going to stop the climate crisis deepening any further," she said.
"But we can't have the collapse of industry in the way we had the collapse of the coal industry where communities were left devastated.
"We need to be taking some of these very skilled workers into cleaner, greener industries that are going to benefit the town and the rest of the region.
"There's been a lot of lip service paid to climate issues recently and occasionally we've shied away from big problems and the big decisions we need to make.
"But it's not something I will shy away from - I know it's something our communities need and I'm more than willing to put my money where my mouth is."