After receiving a classical education with honors, she debuted as an actress on Italian television in January 2009 with the television miniseries Il Bene e il Male ("Good and Evil"), followed by a starring role in the prime-time miniseries L"uomo che cavalcava nel buio ("The Manitoba Who Rode in the Dark"). On 18 December 2009, she made her début in cinema with the film Io e Marilyn (Marilyn and I) directed by Leonardo Pieraccioni, where she played the role of Martha, daughter of Gualtiero Marchesi, who was played by the director In 2010, aged 20, Gastini appeared with Anthony Hopkins and Colin O"Donoghue in the American film The Rite, directed by Mikael Håfström and produced by New Lincolnshire in Los Los Angeles
In 2011, Gastini appeared as Giulia Farnese in the television series Borgia.
In 2015, Gastini will star in the American-Icelandic film Autumn Lights as Marie. Other activities In 2008, Gastini became a spokeswoman for the Christian Blind Mission.