Deni Roberts steered the Bob Mellsop-trained Blaze On in the Direct Trades Supply Pace (2130m) to notch up the milestone.
It was also the 27-year-old's 150th win for the season, as she solidifies her spot in second behind Gary Hall Jnr on the state driver's premiership.
Roberts said there was an element of relief in reaching the milestone.
"I wanted to do it at Gloucester Park," Roberts told The Trots WA.
"I have been thinking about it a little bit off the track, but not too much about it when I'm out on the track.
"Then you have weeks like last week when nothing goes to plan, and I was still thinking to myself I will get there."
Roberts, who scored her first win in 2015, has enjoyed a stellar season and already comfortably passed her tally of 98 wins in 2022.
Among her successes were wins in the John Higgins Memorial with Peter Petrify, Brulee in the Diamond Classic and Street Hawk in the Preux Chevalier Classic.
She has established herself as the stable driver for leading trainers Greg and Skye Bond.
Roberts said the move to the Bond stable took time to adjust to but was now playing a key role in her success.
"I'm pretty settled into it now," she said.
"The first 100 wins of this season I had just taken over at Greg and Skye's.
"I had just taken over off the track there as well and that's the way bigger side of the role.
"A lot of people don't see that side of it, which has its challenges.
"I have handled it, but it did take six months to adjust.
"Greg and Skye have been really good and encouraged me to keep driving with other trainers I've got relationships with."
While Roberts has enjoyed no shortage of success this year, she said she was still her own harshest critic.
"I think my biggest problem is I put a lot of pressure on myself," she said.
"I think sometimes I'm even too harsh on myself and think I could've done this or could've done that.
"Sometimes you have to accept and learn when you stuff up and I think I'm starting to handle that better."
With three months of the season still to run and races like the Golden Slipper, WA Derby, WA Oaks, Golden Nugget and WA Pacing Cup to come, Roberts is set to get the opportunity to score a maiden Group 1 win and close in on 200 wins for the season.
Roberts said she wanted to give herself every chance to meet both targets.
"I've been so set on getting a Group 1 that the 500-win goal almost got pushed to the side," he said.
"I set my goal to get to 100 wins this season and now to think if I pulled my finger out, I could get to 200 is insane.
"If you do the maths then getting to 200 is doable.
"I always try to look ahead because if you don't set goals then you're not looking to achieve anything."
Roberts gets another opportunity for feature race success in Friday's $50,000 Daintys Daughter Classic with WA Oaks contender Turn The Page.
