- At 8, was chosen to play an orphan in a 2000-01 national tour of Annie, and eventually starred in the title role in several productions.
- Made her Broadway debut in 2003 as Baby Louise in the Tony Award-nominated revival of Gypsy, starring Bernadette Peters and directed by Sam Mendes.
- In 2004, helped organize a reunion of Annie touring veterans for a production of the musical in Harleysville, PA, to benefit the Cystic Fibrosis Foundation and Children's Hospital of Philadelphia.
- After she got the part in Gypsy, her mother moved her and her siblings to Manhattan—where they lived for a time on Addison's $70,000 Broadway salary—so she could pursue her acting career.
- Made film debut in Derailed (2005) as the daughter of Clive Owen and Melissa George's characters.
- Appeared in the video for "Check Yes Juliet," a song by Florida pop-punk band We the Kings from their 2007 self-titled debut album.