Lambert, 31, who is currently focusing on herself and her career, was always aware about the possibility of the romance between "The Voice" coaches, reported E! online.
"She was not surprised to hear about the romance between Blake and Gwen. They were always pretty flirty. Miranda and Blake were on the rocks on and off and knew that this could always be a possibility," a source said.
Even after calling it quits, Lambert and Shelton, 39, share a amicable relationship and "Little Red Wagon" songtress has nothing against the Country singer.