Miàn / duì / zhè / fēng / lái / lì / bù / míng / de / xìn / tā / jīng / yí / bù / dìng / bù / gǎn / mǎ / shàng / huí / fù

面对这封来历不明的信，她惊疑不定，不敢马上回复。

Faced with the letter of unknown origin, she was suspicious and unsettled and dared not reply immediately.