The choice of a muted event seems appropriate since she has embarked on her career as a future queen, charged with renovating a monarchy that has become somewhat creaky with age.
"She's done very well, playing a very good supporting role to Prince William and complementing him as part of a team," commentator Robert Jobson said of her first few months as a royal.
The Duke and Duchess Of Cambridge attended the British premiere of the Steven Spielberg film "War Horse" on Sunday night.
The royal couple also invited servicemen and women to the premiere who are members of the duke's regiments. Some 600 current and former members of the British military and their families attended the event.
Palace officials announced this week a few of the charities that the Duchess of Cambridge is supporting, including the Scouts and a group that helps drug addicts. More organizations will follow later, officials said.
She ventured out on her first solo engagement in October - a private charity dinner for about 30 guests - but is yet to make a public speech on her own.
The former Middleton is expected to take on a similar role as the late Princess Diana, who was known for her active support for numerous charities including organizations that helped AIDS patients.
Kate is expected to eventually designate more charities she wants to be involved with as a way for her to carve out her own niche, based on her own priorities and concerns.
She has already taken on an unofficial role as a champion of the British fashion industry, wearing the creations of British designers at home and abroad, showcasing their work in the best possible light.
The Associated Press contributed to this report.