The pair co-star on the drama series "One Tree Hill," which is to wrap up its nine-season run in April.
Bush broke up with Nichols "because she didn't think he was the one," the insider told the celebrity news Web site. "She's moving on."
Bush was previously married to Chad Michael Murray, another "One Tree Hill" cast member, but they divorced in 2005.
2014: The Year in Music [PHOTOS]