Cybill Shepherd should’ve had a poison-taster test the beautifully decorated basket of homemade goodies Martha Stewart sent her just hours after she appeared in the title role of NBC’s “Martha Inc: The Story of Martha Stewart.” The food was fine, but Martha’s handwritten card was a real killer cookie! The lifestyle guru poison-penned that if Cybill ever plays her again she shouldn’t scream so much. “I don’t screech and I don’t scream,” snipped Martha — who cattily advised Cybill to put tea bags under her eyes to get rid of HER ugly bags. (Yeee-ow!) Martha’s note from hell sneered that Cybill “wasn’t convincing” in the role because she didn’t portray Martha as she really is — and somehow made her look phony . . . and SHALLOW?? And the homemade goodies Martha sent Cybill? The star tossed Martha’s cookies, so to speak!