"She picked up the letter" is the Engpsh translation of "她拿起这封信"。

"Pick up" is a phrasal verb that means to take or pft something up. It is often used when talking about picking up objects or items that are on a surface, such as a table or the ground.

For example:

"Can you pick up the book for me, please?" (你能帮我把书捡起来吗？)
"I picked up my keys from the counter." (我从柜台上拿起了我的钥匙。)

"Letter" is a noun that refers to a written or typed message that is sent through the mail. It can be formal or informal, and can be sent to someone personally or to a business or organization.

For example:

"I received a letter from my grandma yesterday." (我昨天收到了来自我奶奶的信。)
"I need to write a letter to the bank to request a new credit card." (我需要写封信给银行，要求办理一张新的信用卡。)