Katelyn Mallyon has followed in the footsteps of Melbourne Cup winner Michelle Payne to become just the second female apprentice outride her claim in Melbourne.

The 21 year-old achieved the milestone aboard Miss Cooper in the Thebigscreencompany.com.au Handicap at Sandown on Wednesday.

Injury and illness robbed Mallyon of almost two years in the saddle and she was concerned she would not gain her 80th metropolitan win before her apprenticeship ended on January 10.

Needing just two winners to outride her claim following her latest injury, Mallyon hit the target on Miss Cooper earlier this month before notching three placings at a Sandown meeting on December 9.

Miss Cooper was expected to give her the milestone win on December 18, but was beaten into third place leaving Mallyon despondent after the ride.

But she returned to scale beaming on Wednesday after leading throughout on Miss Cooper ($5) who scored a half-length win over the $4.20 favourite Maxie's Blue Girl.

Miss Cooper is prepared by Mathew Ellerton and Simon Zahra to whom Mallyon is indentured.

"What a way to do it on one of my bosses' horses and for (Racing Victoria Chairman) David Moodie who has been a great supporter of mine throughout my whole career," Mallyon said.

"It's great to be following in the footsteps of Michelle. Hopefully I can go on to those heights and win a Melbourne Cup one day."

With the milestone now out of the way, Mallyon hopes to add to the tally with rides at Flemington on Friday and Moonee Valley on Saturday.

Mallyon can continue to use her 1.5kg claim on rides she was declared for at acceptance time on Wednesday.

"I hadn't hit the panic button just yet because I've got a nice book of rides on the weekend," she said.

Zahra said it was a good result for the stable.

"To finally outride her claim is a great achievement in this game for women," Zahra said.

"I had a bit of a chat to her after her ride that Friday night and told her to ride naturally like you always have."

While congratulating Mallyon on her milestone, Racing Victoria stewards later relieved her of $200 on a whip-related offence.