She looked at the painting expressionlessly and only said 'blandly' it was okay.

blandly 是形容词 bland 的副词形式。bland 本意是"平淡无味的"，引申为"缺乏感情的、不露声色的"。blandly 表示"平淡地、不带感情色彩地"说话或表达。