She 'went into mourning' for her dead husband. [=she began to mourn for her dead husband]
She is still 'mourning' her husband, who died last year.
She is still 'in mourning' for her dead husband.
(..) is a curious thing. Most curious. Lysa Arryn, for instance. Thoroughly repellant woman. Forgive me. I know you're still in mourning. Lysa was a goo woman. A kin woman. She was neither of those things. We both know it. Still, I pity her son. (..)2015 TvShow: Game of Thrones Title: Unbowed, Unbent, Unbroken Season: 5 Episode 6