Linh, 13, who was not seeded, defeated second seed Manavi Bedi 0-6, 6-4, 10-4 in the quarterfinal and Manasi Bedi 6-2, 6-2 in the last four before crushing third seed Natalia Paiva 6-2, 6-1 to win the girls' 14 title on Wednesday.
Nguyen, her younger brother, and his partner won the boys' 12 doubles event.
The One Love Tennis Labor Day Jr Open was played from September 5 to 9 in Georgia.
Dong Manh Hung, their father, who said he spends around $6,000 a month for their training, revealed that they hope to one day get tennis scholarships to U.S. universities and turn professional.
Last month another Vietnamese, Sophia Huynh Tran Ngoc Nhi, had won the Sleep Houston Summer Junior and Adult Open title in the U.S.