Watson, who turned 18 in April, received her results Thursday. She took three A-level exams: English Literature, History of Art and Geography.
"She's ecstatic," says the source. "She worked really hard and she got the results."
Meanwhile, fans won't see Watson and the gang in Harry Potter and the Half-Blood Prince this Thanksgiving season, as originally expected. The Hollywood Reporter says the movie – originally to be released Nov. 11 – has been pushed back to July 17, 2009.
What's next for Watson?While her GPA qualifies her for Cambridge University – which she's said for years she hopes to attend – Watson hasn't decided yet about whether to enroll right away.
"She's just enjoying her results," a rep for Watson tells PEOPLE. "She's not making any decisions right now."
Watson, one of Hollywood's richest teens, earning a reported $4 million per Potter film, has been in party mode since taking her exams in June. She danced, drank and flirted at the glitzy Cartier Polo Tournament in Windsor in July and has been "living it up" for the past couple of weeks, says a source, adding, "She deserves it."