After you find out you aren't mentally ill, I suggest trying to accept that your reality includes things that others can't see. You will have times when you think you are losing your mind, there is nothing there but imagination, and nothing verifiable. The trick is to prove it to yourself. You can't prove it to the non-believers. They will say you researched this person's life to say they were haunting you. They will say impressions are too vague, they will say you are seeking attention. Try not to let other people's opinion influence your self-worth. If you can get a name or date that you can verify, then you can prove to yourself that it's real. Once you can do that, you can be more comfortable. Don't try to prove it to anyone else.
I went through this period where I doubted myself to the point that I was DRIVING myself crazy. I told my best friend that I thought it was all in my head. She started going on about things we had verified, things other people had seen. I was like, that's not proof! You could be a figment of my imagination, a delusion protecting the other delusions! I don't know what is real. I could be lying in a hospital somewhere with a brain tumor. My entire life could be a fantasy. It went on for a while. I was looking for proof, doubting that proof, and losing my mind. My friends all started calling themselves figments of my imagination, even signing my birthday cards that way. I finally decided that if I was crazy, I wasn't making myself better by worrying about it, so I might as well embrace it. So, I'm crazy. I don't deny it. But my experiences are real to me. I hope you can accept yourself someday. You won't find happiness until you do.
Feel free to email the crazy lady, if you like. You can do it through my profile.