On a day when the Australian challenge fizzled, the world No.77 won through her round-of-16 clash against wildcard Whitney Osuigwe in straight sets.
The 20-year-old needed a tick over 90 minutes for a 6-4 6-1 win against the American.
Joint will now meet the winner of top-seed Ekaterina Alexandrova or fellow Russian Kristina Liutova for a place in the quarter-finals.
Already boasting tournament victories in Rabat and Eastbourne last year, which helped her climb to a career-best No.28 in the world in February this year, Joint lost her serve twice in the opening set but did enough to take it in 45 minutes.
The second set proved more comfortable and Joint, who famously eliminated Serena Williams in the opening round of Wimbledon this year, broke three times to advance.
There was no such joy for Talia Gibson and Storm Hunter though.
Gibson was soundly beaten by German Tatjana Maria 6-0 6-3, while compatriot Storm Hunter succumbed 7-5 7-5 to fifth-seeded Colombian Camila Osorio.
World No.66 Kimberly Birrell, who lost her first-round doubles clash alongside American Peyton Stearns to Ingrid Martins and Ekaterina Ovcharenko 6-4 6-7 (7-4) 11-9, takes on China's Ma Yexin in the singles draw on Tuesday.
In the shock of the day, Swiss third seed Viktorija Golubic was eliminated in three sets by Katie Volynets of the US, while all three unseeded Russian players in action were victorious.
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