The Chicago P.D. star, 32, split earlier this year from Dan Fredinburg, an engineer at Google, a source confirms to PEOPLE.
"They decided to end their relationship in February," says the source. "When you see one another for 24 hours every four weeks, it's impossible to maintain a romantic relationship. They weren't able to spend the time together that was necessary to nurture that kind of relationship."
Bush shoots her hit NBC show in Chicago, and Fredinburg is based in Northern California. The two are "still really good friends," adds the source. "They both care about one another and it was completely amicable."
The actress previously dated her One Tree Hill costar Austin Nichols for several years before splitting in 2012.