(Yahoo!) - It looks like Hilary Duff should start looking for a bridesmaid dress.

Her older sister and constant companion, Haylie, is engaged. On Thursday, the 29-year-old actress made the happy announcement that she will wed her entrepreneur boyfriend of a year and a half, Matt Rosenberg, on her food blog, The Real Girl's Kitchen. "This week has seriously just become the best week of my life!" she wrote on her blog, where just a few hours earlier, she revealed that The Real Girl's Kitchen will become a TV show. "As if announcing The Real Girl's Kitchen TV show wasn't enough, Matt just took me by total surprise and proposed… on April Fool's Day of all days! The moment was genuine and sweet (like him!) and I couldn't wait to say yes!"

"We are so excited and happy to share our wonderful news with everyone," she continued. "We both feel so blessed to have the love and support of our family and friends and can't wait to start this new adventure!"

Haylie flashed a huge rock on her finger in a pic that she posted on Instagram of the newly betrothed couple. "The future Mrs.Rosenberg #Love @mr_sts," Haylie wrote.

Hilary quickly offered her blessing. "So happy to not have to keep this news in!!," she tweeted. "My beautiful sister @HaylieDuff and her amazing boyfriend @Matt_STS are engaged!!!!"

Hailey was maid of honor for Hilary when the younger sister walked down the aisle with hockey player Mike Comrie in August 2010. The two announced their split in January, although they've been seen spending time together — and even vacationing together — with their 2-year-old son Luca.