19-year-old Swede Malja will be making his GP2 debut in place of an ill Rene Binder at the Italian squad, partnering Ferrari protege Raffaele Marciello.
"I have spent the last few days preparing with the team in Italy, and I'm fully aware of the challenge I will be facing this weekend," said Malja, who currently sits 10th in the FR3.5 standings in his rookie season.
"I have yet to drive the GP2 car and will have just 45 minutes of practice on Friday before going into qualifying, so my only target will be to learn as much as possible and to make a solid job for the team."
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Visser will be making her second appearance in GP3 after racing for Hilmer at the opening round of the 2014 season at Barcelona.
She takes the seat at Trident that was occupied by Oscar Tunjo earlier in the season, lining up alongside championship leader Luca Ghiotto and Artur Janosz.
Visser is 19th in the FR3.5 standings, and did claim a front row start for one of the races at Spa in May before being excluded from qualifying a technical infringement.
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