Tyler had written about half of the songs Blurryface had given him. Now, she had laid the foundations for each song, giving him a title, and a few bits of lyrics to work with. He built the rest of the song from that, making sure to send each one to Blurryface via audio file on his phone.
She usually replied with either "YES" or a strange emoticon, one that looked like that: |-/
His bandmates never questioned how he was writing these songs so quickly, or who he was sending them to.
Tyler could only guess they were based on Blurryface's thoughts and life, and from that he deduced that she was a very troubled soul. So far she hadn't shown him that she was malevolent in any way, she was just sad.
Tyler didn't want Blurryface to be sad anymore.
So, he wrote her songs.