The 24-year-old former dancer was out and about in London on Wednesday, wearing a jean jacket and printed headband as she stopped for the sweet treat.
Bonas and Harry, 29, dated for almost two years after being introduced by the royal's cousin, Princess Eugenie.
After Bonas attended her first official function in March, both the Daily Mail and British bookmakers predicted the prince would pop the question soon.
Instead, the couple broke up – with one source saying Harry "found her too needy."
But another pal told PEOPLE the two made "an amicable decision" and are "still the best of friends."
While Bonas heals with a healthy drink, Harry is jetting off to Memphis, Tenn., for a friend's wedding.