How to unmuteva friends conversation

[Android Central Question]

I muted a friend's conversation in messenger on Facebook and now I cannot unsure it. I tried to go to mine and her messages to click on the pencil in the right upper corner, but there was no pencil and there's a message that stays at the bottom of our messages that says that your not able to respond. I did not block her, so if anyone can help me unsure our conversations I would really appreciate it!