in this line the poet's mother laughd at the cardboard picture then became sad after recalling happy memories and the line says "both" because the poet loved to listen his mothe's laughter but was quickly dissapointed as she became lost in her memories
The poet and her mother seemed to have lost a significant thing or person. In the
mother’s case it might be a near and dear one and in the poet’s case it is her mother’s
laughter, happiness and joy.