“I'm 17 and a half now and I'm so thankful to have had the opportunity to grow and learn as a new artist in the spotlight at this time.
“I am thankful for the dialogue around my work and myself and I am thankful to be around such talented new artists.” Some people on Twitter questioned whether Lorde should have qualified for top rock song, but it spent several weeks at the top of Billboard's US Hot Rock Songs chart.
She performed her New Zealand number-one song Tennis Court shortly after winning her second award.
Three of the awards Lorde was nominated for — hot 100 song, digital song and radio song — went to Robin Thicke for his hit Blurred Lines, while Imagine Dragons beat her to four awards — hot 100 artist, rock album, rock artist and streaming song (audio). Katy Perry beat her to top female artist and top digital songs artist, while Justin Timberlake headed her to win top radio songs artist.
Lorde earlier this year won Grammy Awards for best pop solo performance and song of the year awards for Royals, sharing the song of the year award with co-writer and producer Joel Little.