widow
孀 centers on a woman who has lost her husband: a widow.
孀 combines 女 (woman) with 霜, which likely contributes the sound and may evoke the cold, lonely state of widowhood.
A woman 女 beside frost 霜 suggests the cold loneliness of a widow.
For ソウ, imagine a widow sewing alone in a cold room: sew -> ソウ, and the frost outside mirrors her solitude.