When I watched the OVA, I don't know if I should be happy or sad. I also felt so sorry for Shinichi. And almost cried. Haha. I don't want this to happen to Shinichi and Ran. Really the worst nightmare ever. o-o
I think Ran didn't believe him, like she said "Thank you for saying that and trying to make me feel better." It didn't imply something that she believed in him already.
Also, it's Shinichi/Conan's fault whenever Ran's already suspicious of his identity. Because he fools her everytime it happens, making Ran believe that's impossible too. That's why it's not just so easy to believe in what he's saying.
Go! Come with us~ Hahaha