Bound for Rio: Australian Olympian Morgan Mitchell. Credit:Getty Images "Don't think you're the next LeBron James – because you're not," Lois tells her, referring to the NBA megastar. "Just please come home the same person." Mitchell says she has not lost perspective in the last three weeks. "It's healthy banter [from her mother] and it keeps me grounded," she says. "I love the attention. It's nice. But you need to know when to calm down. It's a flattering but at the end of the day I'm still just Morgan. A lot of my friends say, 'Oh my god, you're famous!' It doesn't feel like that. The only reason why I am doing all this [publicity] is because I am running fast. If I am not running fast, it's not going to happen." And she is running fast.

She won the 400m as expected at the nationals but the run many are still talking about came in early March when she took down the crack Jamaican duo of Christine Day and Kaliese Spencer at the IAAF World Challenge meet in her hometown of Melbourne. While Day and Spencer were competing out of season, they are world-class athletes. Before the race, Mitchell told coach Peter Fitzgerald – who competed in the 100m and 200m at the 1976 Montreal Olympics – she wasn't there to just run a personal best. "Let's win it," she told him. "Let's not just run fast – let's win it." Then she did, mowing down Day in the straight.

"They're not in season," Mitchell says, "but I won't lie: it's good to get one on the board." What she didn't realise that night was Freeman and three-time Olympian Melinda Gainsford-Taylor were sitting in the stands, cheering wildly and high-fiving after she had triumphed. Australian athletics has been plagued by politics and ego for so long. It has sadly pushed the athletes worth admiring into the shadows. Now, here stands a shiny new superstar who doesn't think she's LeBron. "Stuff like that is amazing to hear," she says of Freeman and Gainsford-Taylor's support. "When you have two incredible heroes backing you in that way it's amazing." She is being mentored by Freeman, whose husband James Murch is Mitchell's manager.

Mitchell was just five years old when Freeman produced her nation-defining win in the 400m at the Sydney Olympics. Thank God for YouTube, so her understudy can watch the race. And thank God for Cathy. A woman of very few words, she has given Mitchell two invaluable pieces of very simple advice. "She tells me, 'Just be happy'," says Mitchell. "That, and 'breathe'. She always tells me to breathe. Control your breathing, control your emotions, you'll be fine. You're not going into battle with an AK47 – it's just running. When she simplifies that for me, it makes it much easier." Mitchell's emergence can also be attributed to her dramatic change in body shape. She body shamed herself in late February when she …

"Where I say I was an elephant?" she butts in, finishing the question before you even ask it. She has ripped 3kg off her frame. Tell her she wasn't really an "elephant" and she laughs. "I know! It's just something I said at the time. I thought it was pretty funny. Looking back, I was thinking, 'I'm massive'. I don't want girls to read this and start thinking they should starve themselves. It wasn't about that. It was about getting as lean as I could this year to run fast. I never try to lose weight for image. I was perfectly happy with my body until I realised I had to get slimmer to get where I wanted and that was the Olympics." While much has been made about her physique, what hasn't been widely reported is that she has turned vegan. "A lot of people laugh at me for that," she says. "I have been vegan for a year and a half. That's really helped with everything: energy, health, the environment. I am one of those people who actually cares. It's what I chose to do."

Others athletes might cock an eyebrow, wondering how she finds enough protein and carbs to propel her down the track – but it's not unheard of. Carl Lewis credited his form in 1991 to a vegan diet, although cynics might suggest other substances were at play. The legendary Murray Rose won four Olympic gold medals for Australia in the 1950s and 60s. He was a vegan from childhood and was known as the "Seaweed Streak". "I love it because you can always eat when you are a vegan," Mitchell laughs. "I'll wake up, I'll have two pieces of banana with maple syrup, peanut butter on rye bread and then a smoothie, which will have every vegetable and fruit that you can imagine. "Then, for a snack, I will have a chia pod and some dates. I'll have a tofu burger and some rice for lunch. And I'll make something up for dinner: a vegan pizza with vegan cheese or noodles. When you learn to love it, it comes easy.

"It's quite funny thinking about the amount of food I eat. I went from being an elephant to this toned athlete who can still eat as much as she wants as long it is the right food." Whatever she's eating, it's working. As the countdown to Rio cranks up, expect to see more of the thousand-watt smile. And when she gets there also expect her to seek out LeBron, who is likely to suit up for the US Dream Team for his fourth Olympics. "If I met LeBron in Rio, I would faint and not wake up for a year," she laughs. "Let's make it happen. He's pretty humble, though, isn't he?"