I think everyone should have a pen friend and write email messages to each her.

我认为每个人都应该交一个笔友 并互相发送电子邮件

I have a pen friend.

我有个笔友。

I have a pen friend in America.

我在美国有一个笔友。

Hello. I'm your new pen friend.

你好。我是你的新笔友。

Who can be your pen friend? Sam.

谁能做你的笔友？

I want to be her pen friend.

我想成为她的笔友。