Is expiation obligatory for one who copied her friend's statement: "Say, 'By God, I did not lie,'" and sent it to her without the intention of swearing, but her friend believed she had sworn?

An oath is not constituted by writing without the intention of an oath, and therefore, no expiation is required due to the non-constitution of the oath. For the ruling on using tawriya (ambiguous language) for this purpose, please refer to Fatwa no. 138838.