They broke up, her rep told ABC News.
The "Modern Family" star, 23, began dating Prokop, 24, when they both auditioned for "High School Musical 3" in 2008, People reported. They went on to co-star in "Geek Charming" on the Disney Channel.
"We had our first formal date at Casa Vega, this little Mexican place. We got to talking and I think it was on the date that we realized we didn't have to work to impress each other," he told Seventeen in 2012. "We were both there for the right reasons. It just felt so natural."
In 2011, Hyland revealed on "The View" that the two were living together.
"Pros: It's cheaper," she said, according to reports. "Cons: We're both really lazy. So, laundry and dishes, we complain about that."