Need advice on an odd and serious psychological problem?

The crush you are experiencing is not in the least bit weird. It is like many of the celebrity crushes people experience that are unrequited and not worrisome. In fact, I know a few girls who have crushes on the rockstar Kurt Cobain who died in 1994. Even though he's a more recent person, I don't think it'd be any less relevant. You are infatuated with who she was as a person and she seems personified to you because you are reading a diary that she wrote. As long as you don't let your feelings for her stop you from dating other people you will be just fine. And indeed, you DO have control of that, whether or not you realize this.