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.
(..) You've declared for other houses before, Lord Baelish. It's never stopped you from serving yourself. The past is gone for good. You can sit here mourning its departure or you can prepare for the future. You, my love, are the future of House Stark. Who should the North rally behind? (..)2016 TvShow: Game of Thrones Title: The Winds of Winter Season: 6 Episode 10