But when the milestone arrived, it came with a flurry.

O'Sullivan notched up the ton with her victory aboard the David Aiken-trained Mighty Flying Art at Cobram last Thursday.

It was the third of a trio wins in three-straight trips to the racetrack for the 22-year-old from Heathcote, whose career in the sulky launched during the 2017-18 season.

A purple patch for the girl in the purple and white helmet kicked off at Cranbourne the previous Sunday with a win for Tyabb trainer Geoff Clout aboard My Superannuation and continued with a victory aboard Neanger Guy at Bendigo on Wednesday.

The milestone was clinched with her next drive at Cobram and ticked off a long-sought-after goal.

"It's been a goal for a while, so it was great to finally be able to reach it," O'Sullivan said.

"It's taken a little bit longer than I expected, but I'm glad I got there in the end.

"It was something I probably wanted to reach last season, but wasn't able to. But once that didn't happen, I was pretty eager to get it done early this season.

"I got put on the sidelines there for a little bit, so that prevented me from getting there a bit quicker, but it was great to tick it off.

"Three wins in three days at the races is always nice, so in one way, I probably got there a little quicker than I thought I might have."

Ever-grateful for the opportunities that flow her way, O'Sullivan was content for the milestone to arrive in any way possible.

Albeit, she did have reason to hope that it may have come a day earlier with Neanger Guy, who is trained by her father and still the biggest influence on her career, Gordon Rothacker medallist Jim O'Sullivan.

The eight-year-old gelding has accounted for five of O'Sullivan's 100 wins, including one of her biggest, on Ballarat Pacing Cup night in 2020.

"He's a lovely horse. We love him and he just does a great job out there," she said.

"This preparation he's become a bit more dynamic and a bit more versatile, where you don't just have to lead with him, you can come from behind and win.

"He's been going super. I didn't think we were going to win (last Wednesday), I didn't go into it very confidently, but everything just worked out."

While dad's impact on her career has been more than profound, O'Sullivan says she's lucky to have benefited from the experience and expertise of a few of her fellow drivers.

"There have been a few drivers like Michael Bellman and Greg Sugars, who have always been in my corner and have helped me with everything," she said.

"Of late - and he probably doesn't know it - Bailey (McDonough) has been really great. He has got a lot of knowledge and I tend to go to him first and ask about my driving and what I could have done differently.

"He never puts you down, he just informs you what you could have done.

"It's really been helpful, even though I'm not really sure he's aware of it."

O'Sullivan's eight wins this season have come from 58 drives at a winning strike rate of 14 per cent.

It followed 31 wins last season and 40 in the extended 2019-20 season.

O'Sullivan rates her wins in the 2019 Elmore Pacing Cup aboard Fourstarzzspecial, also trained by her father, and on Kissmelvis at Melton in June last year as among her most cherished.

She is unlikely to ever forget her first winner as it was achieved in a non-metro race at harness racing headquarters aboard the Neville Pangrazio-trained Showgun Thomas.

She was 18 at the time.

READ MORE: Heathcote harness racing driver Shannon O'Sullivan breaks through for first win

As for the best horse she has sat behind, that honour goes to the Kate Hargreaves-trained Group 1-winner Dont Care, albeit she has never actually driven him in a race.

"As a trotter, he was very cool to drive and I'd love to get an opportunity one day to drive him in a race," she said.

"I think there are only four people, who have driven him, Ellen (Tormey), Alex (Ashwood) and Kate (Hargreaves) and myself in track work.

"It was something in hold pretty close to my heart."

O'Sullivan is continuing to combine race driving with tertiary study and is getting closer to completing her degree in exercise in science.

While she acknowledges it's a heavy workload, she has definitely embraced the challenge.

"At the moment I am handling it really well. We're nearly halfway through the semester and it hasn't worried me too much," she said.

"There are some meetings that I had to say no to because I have uni on that day.

"I haven't lost any really big opportunities because of it.

"It's great there are trainers and owners out there still prepared to back me and put me on their horses.

"Hopefully they can see me driving confidently and keep putting me on."

O'Sullivan has added another string to her bow this year by becoming a panellist on TrotsVision's regular weekend coverage.

She is clearly relishing the involvement.

"I am really enjoying it - I love the media side of it all," she said.

"I'm really grateful HRV (Harness Racing Victoria) has given me the opportunity to do it and to help get my name out there.

"I'm looking forward to seeing where it leads."

As for her future in the sulky, O'Sullivan has already set herself a new goal.

"Hopefully the next 100 come up quicker than the first 100," she said.

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