Their match was interrupted by rain, making it difficult for both to keep their focus - but eventually the world No. 1 came through 6-2, 3-6, 6-2.
The world No.1 admitted: "It's not easy when a match is suspended and you have so much time between [sessions of play]."
She added that she was satisfied with her performance - despite being forced to a decider by her American opponent.
"At the end, I won the match, and this is what counts for me," she said, but she was quick to give credit to Chirico.
"It's always tough playing someone you've never played -- I think she played very well yesterday but also today."