"Best Days of Your Life" is a song written and performed by American country artist Kellie Pickler, and co-written by Taylor Swift.
 It was released on December 1, 2008 as the second single from her self-titled second album.
 Swift also provides background vocals on the song.
 The song is about a narrator explaining how her former boyfriend cheated on her and moved on to a new girlfriend to start a family with, wishing them well on their new life but says that the new girl won't top what they previously once had before.
"Things That Never Cross a Man's Mind" is a song written by Tim Johnson, Don Poythress and Wynn Varble, and recorded by American country artist Kellie Pickler.
 It was released as the third and final single from her debut album, "Small Town Girl".
"I Wonder" is a song written by Chris Lindsey, Aimee Mayo, Karyn Rochelle, and co-written and recorded by American country artist Kellie Pickler.
 It was released as the second single from her debut album "Small Town Girl" (2006), on February 5, 2007.
"Red High Heels" is a song written by Chris Lindsey, Aimee Mayo, Karyn Rochelle, and co-written and recorded by American country artist Kellie Pickler.
 The song was the debut single off her debut album "Small Town Girl" (2006).
"100 Proof" is a song recorded by American country artist Kellie Pickler.
 It was released on April 16, 2012, and served as the second single from the album of the same name.
 It was written by Leslie Satcher and James T. Slater, the same writers that wrote the album's first single "Tough".
 "100 Proof" uses an analogy between love and alcohol levels, as if its addictive.
 The song was Pickler's first to not reach the Top 40 on the "Billboard" Hot Country Songs chart, peaking at number 50 instead.
"Makin' Me Fall in Love Again" is a song written by Karyn Rochelle, James T. Slater, and Shane Stevens, and recorded by American country artist Kellie Pickler.
 It was released in April 2010 as the fourth single from her self-titled second album.
 The song is about someone being in love and still having that feeling, despite being told that it will fade away.
 Pickler said that it reflected her current relationship.
Kellie Pickler is the self-titled second studio album by American country artist Kellie Pickler.
 The lead-off single, "Don't You Know You're Beautiful", was debuted at the 43rd Academy Of Country Music awards and peaked at 21 on Hot Country Songs.
 The album was released via BNA Records/19 Recordings on September 30, 2008.
 Since the albums' release, three more singles have charted; "Best Days of Your Life" at number 9 (which was co-wrote with fellow country artist Taylor Swift), "Didn't You Know How Much I Loved You" at number 14 (a re-recording of an album cut from Pickler's debut album "Small Town Girl") and "Makin' Me Fall in Love Again" at number 30.
"Didn't You Know How Much I Loved You" is a song written by Chris Lindsey, Aimee Mayo, and Troy Verges, and recorded by American country artist Kellie Pickler.
 It was released in August 2009 as the third single from her self-titled second album, and her sixth single release overall.
 The song is a ballad where a narrator describes her lost love, responding to him with said song title as a question.
"Don't You Know You're Beautiful" is a song written by Chris Lindsey, Aimee Mayo, and Karyn Rochelle (who co-wrote her previous hits "Red High Heels" and "I Wonder"), and recorded by American country artist Kellie Pickler.
 It served as the lead-off single to her self-titled second album.
 Pickler debuted the song at the 43rd annual Academy of Country Music Awards, and it was officially released to radio in June as the fourth single of her career.
100 Proof is the third studio album by American country music artist Kellie Pickler.
 It was released on January 24, 2012.
 The album includes the single "Tough".
 The title track, was released exclusively on iTunes on December 20, 2011.
 The album sold 27,000 copies in the first week, and is the highest-charting album of Pickler's career on the "Billboard" 200 and the Digital Albums chart.

Question: Kellie Pickler is the self-titled second studio album by the American country artist, Since the albums' release, three more singles have charted; including which song, written and performed by American country artist Kellie Pickler, and co-written by Taylor Swift, at number 9?
Answer: Best Days of Your Life