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The One Tree Hill star, who split from her former co-star and boyfriend of more than six years Austin Nichols last February, struck down speculation that she and the That '70s Show star, 34, are anything but friends.
"Topher has been one of my dearest friends for six years. We have coffee all the time, and he is actually a great sounding board for me with sort of how to be prepared with all things sitcom," Bush, 30, told Us Weekly at a TCA press event for her new series Partners Sunday.
Grace and Bush had been photographed just two days earlier having coffee together at West Hollywood's Coffee Commissary.
Bush has a history of hooking up with her co-stars. In addition to her six-year romance with Nichols, she was married to Chad Michael Murray in 2005 and also dated another OTH cast member, James Lafferty.
As for the That '70s Show cast, the most prominent couple to emerge from the show is the current rumored fling between Mila Kunis and Ashton Kutcher, who've been denying their speculated relationship since last April.