"I'm still shocked," she told Fairfax Media. "Yesterday was a very, very bad day for me, because no-one can feel good about this situation.
"I was crying after for one hour and a half non-stop. I was crying so much.
"I know, and all the people who know me, they know I did nothing wrong."
Viviani, whose punishment also saw her removed from the doubles competition, insisted there was no malice in her move and the boy was not bothered.
"I was enjoying the game," Viviani said. "The kid was moving and I hit him.
"I said sorry immediately, because I saw him, but he was OK. He was standing with the balls in his hands waiting for the match to start again."
Former Italian pro Maria Elena Camerin, who mentors juniors from her home country, was furious at Viviani's treatment.
"I've never seen something like this. I was on court and I said, 'C'mon, we are here from Italy and now she can't play for this kind of stupid thing?'," Camerin told Fairfax.
"It is not cheap for her to come here all the way from Italy. We've been here from January 4.
"She was crying all day. It was very sad. She's a very nice girl.
"I just said to her, 'S*** happens'."
Wang automatically progressed to a second-round match against Swiss first seed Rebeka Masarova, prompting angry reaction on social media.
"Terrible decision to default Maria Vittoria Viviani. The offending umpire should be defaulted from the competition," one wrote on Twitter.
Another called the decision utterly absurd. "Sorry for the disqualification today. One thing ABSURD. Always future champion ahead!"
"What a load of bs! She hit it softly and clearly wasn't trying to hit and hurt the ball boy. Joke."
Others suggested there was an element of double standards, when Kei Nishikori also hit a ball kid with a tennis ball during his five-set defeat to Roger Federer on Rod Laver Arena, but did not suffer the same fate as Viviani.
"Both Nishikori & a female junior swatted balls away, making contact w ball kid. But only one of them was DQ-ed!"
Viviani is the 117th ranked female junior in the world and won't remember this trip Down Under fondly, after also losing in the first round of the Traralgon Junior International.