She made her acting debut in the television pilot of American Men (2006) and played her first major-film role in Annie (2014). Colletti appeared in 2018 films Wildlife and Skin before garnering critical praise in the lead role of Stella Nicholls in horror film Scary Stories to Tell in the Dark (2019). She achieved further recognition and plaudits as Dakota in the sixth season of horror drama series Fear the Walking Dead (2020–2021) and the Truth Pixie in fantasy film A Boy Called Christmas (2021). In 2022 she portrayed Lucy in the second season of Only Murders in the Building. She also starred in the Netflix series Boo Bitch.