Gaines took over from Nev Power as CEO in February 2018, with many suggesting Power was exiting at the peak of FMG's success.
While that's not been the case, it would be easy to solely attribute FMG's stellar FY19 to increasing iron ore prices.
Even with a flat year-on-year iron ore price in the first half of FY20, FMG boosted its half-year dividend by 150% to A30c per share.
The company also launched a buy-back late last year, all while continuing to reduce debt.
Market conditions in 2018 had seen discounts for FMG's lower grade iron ore widen, which put margins under pressure.
Instead of sitting back and waiting for conditions to improve - which FMG always maintained they would - the company brought forward the introduction of its new West Pilbara Fines (WPF) product.
The introduction of WPF combined with a narrowing discount and overall iron ore price rise saw FMG's average realised price jump 47% in the March quarter to US$71 per tonne.
Gaines recently said the company felt vindicated by the reversal after long maintaining the increased discounts for lower grade ore was cyclical rather than structural.
FMG reports its June quarter and full-year production results on Thursday, with the average realised price tipped to rise again.
The improving conditions, and the looming federal election, where a Labor win would have seen a change to franking credits, saw FMG get on the front foot and declare a fully franked A60c per share dividend in May.
Gaines hasn't ruled out further shareholder returns when the company reports its full-year financials next month.
Gaines was born in Derby in Western Australia's remote Kimberley region but a successful career as a chartered accountant took her beyond Perth to Sydney and London.
She was a former CEO of Helloworld and Heytesbury, with the latter role giving her exposure to John Holland and the themes of safety and major project delivery.
Gaines first joined the board of FMG in 2013 as its first female director, and became chief financial officer in 2017.
She said she'd followed FMG from afar.
"I was working in London, then in Sydney, so I admired the success of the company and then I had the opportunity to meet with the chairman Andrew Forrest and the then-CEO Nev Power and other board directors, and I felt a very strong alignment with the culture," she told MNN.
"And I think the vision for the company was very clear and that was a strong attraction for me to join the board."
Gaines was announced as Power's predecessor in November 2017, leading a new-look management team of Julie Shuttleworth as deputy CEO, Greg Lilleyman as chief operating officer and Ian Wells as CFO.
The four sit side-by-side in an open plan office at FMG's East Perth headquarters.
"We all have our own areas of responsibilities but then we come together as a leadership team and we collaborate, we talk about the decisions we're making, make sure they're the right decisions in the short-to-medium-term, as well as the long-term," Gaines said.
"We just have a team of people who are highly motivated, very professional, very engaged and we're all very closely aligned on the various outcomes, and we come together, each with our own areas of expertise and experience, and I think that really is a very powerful combination."
While Gaines has certainly ticked a few goals off her list with the introduction of WPF, the start of construction of the US$1.25 billion Eliwana project and the approval of the Iron Bridge magnetite project, she noted a key highlight of the past year.
"I think one of the key highlights is we've recently surveyed our staff, as we do every year in an annual safety and culture survey, and we've again had a very high participation rate," she said.
"What that's demonstrated is the culture and values at Fortescue, and that strong alignment with safety outcomes, is still just as relevant, and I think that's really key to the successful performance at Fortescue.
"We've seen ongoing improvement in our safety performance as well, which is absolutely critical."
Gaines said the challenges of business are what made it interesting.
"It's maintaining that momentum and with that significant investment pipeline, that does bring challenges as well as opportunities," she said.
"We are creating jobs in WA, we're continue to contribute to the economy of the state and Australia, so I think those are all the opportunities and positives and the challenges that come with that - we're managing large-scale projects, we need to make sure we keep our staff engaged, alignment of values, we deliver on our safety outcomes, and like a lot of us in the sector, there are some cost pressures.
"We don't think it's anything that's untoward at all, but we have to stay frugal, we have to maintain our low-cost leadership position, because the market will go through cycles, and again, you can't be complacent in what's seen to be a strong market about those core fundamentals which for us, are about being low-cost, because we continue to generate very strong margins and we can do that through all market cycles."
Growth is certainly on the agenda for Gaines' FMG, as evidenced by the recent approval of the US$2.6 billion Iron Bridge magnetite project.
"It's a genuine growth initiative. It's a new product for us, it's incremental to our existing hematite operations, it gives us great optionality and delivers on our strategy, more importantly," she said.
Gaines has also expressed a desire for FMG to grow through exploration and potentially diversify.
The FMG board recently returned from Ecuador, where the company has just started drilling. It recently acquired an Argentinean explorer and has established offices in Quito and Buenos Aires.
FMG also recently signed a farm-in with Strategic Energy Resources in South Australia worth up to A$11 million.
Gaines acknowledged the best way to unlock value was through exploration, but it was something that would take time.
"Certainly, I think we're all pretty excited about the exploration opportunities, and I think the great thing is we've got very good geologists who have experience in a range of commodities who can actually run with those programs and that way, we're not distracting anybody from our core iron ore business," she said.
"We're all pretty excited about what those opportunities might uncover, but again, it's not distracting us from our core objectives."
Gaines feels fortunate her career has given her the opportunity to work with two of WA's leading business and community leaders, Forrest and Janet Holmes a Court.
"I've gotten work with them closely and I've found their approach to not only business, but philanthropy, has been really inspiring," she said.
"I think this genuine view that business is not just about the bottom line - obviously the bottom line's really important and we've got a lot of stakeholders who depend on us achieving our results - but it is about that broader community engagement.
"There's no point a business being successful if the communities in which we operate aren't successful.
"That view of giving back, of helping people in regional areas, particularly to succeed, and our whole approach to employment and engagement with Aboriginal people and also our Billion Opportunities program have been really inspirational, and that's because of the vision of Andrew.
"I find that leadership style around looking at the broader community engagement as very inspirational."
The admiration is mutual with Forrest praising Gaines earlier this month.
"She's proving to be such a very talented leader of our team and I'm delighted to have her step up from the big shoulders of Nev Power, who stepped up from the kind of middling job I did, and to say that I'm really proud that the future of our company is in the hands of Elizabeth and the core leadership team," he said.
FMG CEO Elizabeth Gaines is nominated for CEO of the Year in the 2019 MNN Awards.