Despite being over 20 years late to Neon Genesis Evangelion, it quickly became one of my all-time favorite anime series. This is for a multitude of reasons including but not limited to Rei Ayanami.
As someone who suffers from dissociative episodes as well as being on the autism spectrum, Rei's struggles resonated with me on a personal level. This combined with her eye-catching design and her role in the End of Evangelion made her my favorite character. Perhaps fixating on a fictional character to this extent goes against the anti-escapist message Anno intended with Evangelion. However, I'd like to think that Rei has motivated me to work on bettering my relationships with other people, as well as becoming more assertive. I root for the Evangelion cast's happiness because I want to be happy. If Rei can learn to form bonds with people, and value herself, then maybe I can too.
Beyond the incestuous implications of ReiShin, I feel that Rei being in a romantic relationship with Shinji would undermine her character. Furthermore, I don't think that the majority of the Evangelion cast are capable of having healthy relationships. Yes, that goes for KawoShin and AsuShin as well. However with time, I like the idea of Rei and the other EVA-pilots ending up as good friends. I suppose that's part of the tragedy of Evangelion, apart from Shinji, she never got a chance to foster those kinds of friendships.
"You're nothing but an object living a lie, pretending to be a person. See? There's a dark part of your heart inside you that you can see nothing of, that you know nothing of. That's where the real you is."Rei III
"He's not going to need me anymore. He's going to abandon me. I thought I had wished for that day to come, but... now, I am afraid."Hideaki Anno
"Rei is someone who is aware of the fact that even if she dies, there'll be another to replace her, so she doesn't value her life very highly. Her presence, her existence, "ostensible existence," is ephemeral. She's a very sad girl. She only has the barest minimum of what she needs to have. She's damaged in some way; she hurts herself. She doesn't need friends."
/c/'s Rei Archive
Theory and Analysis: Rei Ayanami (In-Depth) - Evageeks