The 25-year-old actress -- daughter of NBC News anchor Brian Williams -- has been dating Van Veen for three years. He's the co-founder of the popular site College Humor, and was chosen as one of Crain's New York's 40 Under 40 in 2012.
Williams, for her part, recently told Glamour magazine that she hoped to settle down and have a family in the not-too-distant future. "My goal is to create a career I can walk away from and become a mom," she said in the March issue. "I'd love to be a mom -- and not have to bring my kids into my trailer."
This will be the first marriage for both Williams and Van Veen, who recently returned from a trip to Colombia. Two days before news of their engagement broke on Feb. 26, they were spotted sharing an ice cream sundae at the Tower Bar at Sunset Tower.