When I finally finished the series I was completely broken. Everything I thought I knew about her- a quiet and weird girl who's really full of emotion that she doesn't really understand- was completely shattered with the whole revelation about the clones, and Lilith and Yui and hell, everything- not to mention the fact that she doesn't even get a proper happy ending.
I became pretty depressed for a long time after that. I ended up cutting a friendship because of it since one of my friends wanted me to 'snap out of' my thing for Rei and I just didn't want to.
I didn't stop with my obsession- I kept collecting pictures, looking at merchandise- I even did some writing to make myself feel better and though it helped, I was still hurt.
In the end, I lost my job and pulled myself away from my friends (for a while I only saw them every few weeks instead of every weekend) and continued to surround myself with pictures of her to help me escape from the horrible spiral that my obsession was causing.