3 sentences for 回信 (huí​xìn — to reply to a letter)

1. 她没有给他回信。

   tā méi​yǒu gěi tā huí xìn.

   She didn't write back to him.

   Source: Tatoeba

2. 我回信去感谢她。

   wǒ huí xìn qù gǎn​xiè tā.

   I wrote back to thank her.

   Source: CCMatrix

3. 我写信给他们，但对方没回信。

   wǒ xiě xìn gěi tā​men, dàn duì​fāng méi huí xìn.

   I wrote to them, but they didn’t reply.

   Source: UM-Corpus: News