The True Blood star used the cane for assistance as she posed for photographers at the New York premiere of her movie A Bit of Light with her husband Stephen Moyer, who directed the independent drama. The 41-year-old told People that it's been a "difficult" two years as she has been dealing with undisclosed health issues that have left her with mobility and speech difficulties. "It hasn't been easy.” A source told the outlet that The Piano actress will hopefully make a full recover. Despite her ongoing health battle…