Collins was born in Guildford, Surrey. She is the daughter of English musician Phil Collins and his second wife, Jill Tavelman, an American who is the former president of the Beverly Hills Women’s Club. After her parents’ divorce when she was five, Collins moved to Los Angeles with her mother. She graduated from Harvard-Westlake School and attended the University of Southern California, majoring in broadcast journalism. She was presented as a debutante at the Bal des débutantes in Paris in 2007. Collins is the half-sister of actress Joely Collins and musician Simon Collins from her father’s first marriage, and Nicholas and Matthew Collins from her father’s third marriage.

Collins began acting at the age of two in the BBC series Growing Pains. As a teenager, Collins wrote a column, “NY Confidential”, for the British magazine Elle Girl. She has also written for Seventeen, Teen Vogue, and the Los Angeles Times. She was selected by Chanel to wear one of their gowns at the 2007 Bal des débutantes at the Hôtel de Crillon in Paris, which was featured on season three of the reality television series The Hills. She was picked by Spain’s Glamour magazine in 2008 as its International Model of the Year, and appeared on the magazine’s cover in August 2009. Collins covered the 2008 US presidential election as a host on the Nickelodeon series Kids Pick the President. She won a 2008 Young Hollywood Award for Newest Red Carpet Correspondent.

In 2009, Collins appeared in two episodes of the teen drama series 90210, including the first season’s finale. Collins was one of 20 women named by Maxim magazine as one of the Hottest Daughters of Rock Stars in 2009. In 2009, Collins co-starred in the film The Blind Side as Collins Tuohy, the daughter of Sandra Bullock’s character Leigh Anne Tuohy. In 2011, she played the warrior priest’s daughter Lucy in the thriller Priest, opposite Paul Bettany. MTV Networks’ NextMovie.com named her one of the Breakout Stars to Watch for in 2011. She co-starred in the 2011 action film Abduction with Taylor Lautner.

The following year, Collins played Snow White in Mirror Mirror, an adaptation of the fairytale Snow White and the Seven Dwarfs, co-starring Julia Roberts as the Evil Queen Clementianna. Robbie Collin from the British newspaper The Daily Telegraph wrote of Collins: “She has an adorable, sensational, almost perfect face for cinema; think Audrey Hepburn with the eyebrows of Liam Gallagher. Her smile is the platonic ideal of cheeky.” She made her singing debut in the film, performing an English re-written cover of “I Believe (in Love)”. Collins was reportedly cast as the lead in the 2013 remake of Evil Dead, but dropped out due to a scheduling issue. In March 2012, it was announced that Collins would portray Samantha in Stuck in Love, starring alongside Jennifer Connelly, Logan Lerman, and Greg Kinnear.

Collins then starred as Clary Fray in The Mortal Instruments: City of Bones, a film adaptation of the first book in The New York Times best-selling The Mortal Instruments novels, written by Cassandra Clare. In October 2013, Collins appeared in the music video for “City of Angels” by Thirty Seconds to Mars. In 2014, Collins starred as Rosie Dunne in the film adaptation of Love, Rosie, also known as Where Rainbows End, written by Cecelia Ahern. She appeared alongside Sam Claflin. Collins is expected to have a leading role alongside Alden Ehrenreich in the upcoming romantic comedy-drama Rules Don’t Apply from Warren Beatty. In March 2016, Collins joined the anorexia drama film To the Bone in the lead role, written and directed by Marti Noxon. That same month, she was cast in the Netflix drama film Okja alongside Jake Gyllenhaal and Tilda Swinton, directed by Bong Joon-ho.

Collins is an outspoken anti-bullying advocate and is serving as a Celebrity Ambassador to anti-bullying organization Bystander Revolution, founded by author MacKenzie Bezos.