Mackenzie Shirilla isn't getting her day in court ... because her latest appeal was denied, TMZ has learned.

According to new court docs obtained by TMZ, Mackenzie's appeal was not accepted for review.

The papers say the judge dissented and the court declined to accept jurisdiction over the case. Basically ... they declined to hear the case and it was dismissed.

As you know, Shirilla is doing time for killing Dominic Russo and Davion Flanagan by driving her car at 100 mph straight into a brick wall. This was her second appeal since she was convicted and sentenced in 2023.

We broke the story ... Mackenzie had been bored as hell behind bars, but we've recently learned that she's got a job in jail as a food service worker.

Mackenzie's serving two concurrent life sentences with the possibility of parole after 15 years ... which probably feels even longer now that her second attempt at an appeal's been denied.