[4] MacNeil began her acting career at a young age and appeared in her first significant film production in a non-negligible marginal role.
The following year, MacNeil had her international breakthrough when she was cast in the role months before as "Patty Farrell" in the first film adaptation of the successful book series Diary of a Wimpy Kid.
In 2012, MacNeil had a guest role on RL Stine's The Haunting Hour and made an appearance in an episode of Falling Skies.
In 2013, MacNeil appeared on Canadian-American horror film Horns starring Daniel Radcliffe, where she played the role of young Glenna.
MacNeil was nominated on 2015 for the 36th Young Artist Awards in the category of "Best Performance in a TV Series - Guest Starring Young Actress 17-21" and the Joey Awards in the category of "Best Actress in a TV Drama Guest Starring Role Age 14-18 Years" for her work on Strange Empire.
[citation needed] That same year, MacNeil appeared on the American movie The Edge of Seventeen, starring Hailee Steinfeld, Woody Harrelson, Kyra Sedgwick and Haley Lu Richardson, playing a TCBY girl.