One of my many favorite scenes, is when MC locks Erynn and Lexi into the room and even threatens to get them a bathroom bucket if they take too long. There's a lot of fantastic storytelling scenes with Erynn if you go sole Lexi path.It's hard to say, but the indication seems to be that he was Erynn's shadow. He wouldn't have been there if Ethan or Alexis had their druthers. Erynn was probably right when she said that. That being said, that legit has nothing to do with the present, and I think even Erynn realizes she was being irrational in calling dibs on Mc because she knew him in the past and being mad at Alexis for going after him.
And yeah, he was Erynn's shadow. They were best friends, she even dressed him up in her clothes and makeup. There is at least one scene where he sees a picture of himself dressed up.
And on the Lexi path when Erynn and her have their argument that Lexi makes it sound like Erynn didn't fully grasp some elements. I still think it comes down to her being too shy within the group dynamics.