Victim identified as Ruqia Hassan, who regularly shared information about daily lives of residents living under ISIS stronghold Raqqa in Syria under the pen name Nissan Ibrahim.
She was executed by the group after they alleged her of spying on them. It is not clear when was arrested by the ISIS.
'Go ahead and cut off the internet, our messenger pigeons won't complain,' Ms Hassan wrote for the final time, maintaining her good sense of humour and hope even during the most difficult of times.
Ruqia's family got to know about her death three days ago and were told she was found guilty of carrying out counts of espionage.
ISIS has executed many people who dare to speak against their rule or providing intelligence information about their movements in Raqqa.