Eve having a striking 250px-Eve2.jpgMillea.jpgTeitoChildMother.jpgTeitoKlein.jpgresemblance to Teito and Millea Klein (Teito's mother). I believe that one of the two has Eve's soul. Teito is considered as Eve's reincarnation, due to their similarity in physical appearance and personality, and also when Verloren's scythe said, "I've been looking for you for such a long time." However, it is truly unknown.
Millea is in her mid 30s having giving birth to Teito and him being 15 years of age. So she is slightly older than Ayanami. When Eve died she was reincarnated and lived in the human world, Verloren attacked many souls on Earth trying to find her until his soul was reincarnated to what is now Ayanami. And Ayanami had trouble finding her Millea due to her being poisoned and living in a secret room hidden by Ouka's Father. Also it is now known that Wolfram poisoned due to the Shadow Man's guidance and is currently unknown to as of why he did so.
I know some of the ideas and facts given in this may be a little off but this is from my current researching.
Please comment and let me hear your ideas as to who is Eve's Reincarnation.