It happened a few years ago that I begot the courage to tell someone special that I was interested in her, however she did not share the same feelings. We continued to talk with each for a few months, and really seemed to get along. During the course of this time I had dreams about us finding each other like family long been separated, enjoying a first date, having heated arguments, making love for the first time (became lucid, and quickly woke up lol) and seeing what I knew was our first and only child together, basically a whole lifetime with her in a few short dreams. I soon discovered that this person had blog in which she expressed similar dreams about someone that "she could not mention", even saying that she messed things up with this person and wanted to correct the situation. I couldn't help but feel it was about me, and soon after I had a dream in which she revealed to me that she liked me. I was hurt by how she had rejected me in the past, so I gave her the very same response she gave to me. She didn't take it very well and walked away. She appeared to me in dreams a few more times after that, upset and even crying. When I checked her blog some time later she expressed that she did not want to rekindle with this person, because she already knew what his answer was going to be. We stopped talking after that, but our actual relationship didn't end on a bad note.
I'm wondering If what I saw with her was a precognitive dream of what could have been, or what will indeed happen in the future? I know it doesn't help that we did in fact connect with each other in dream, and I rejected her. It's very upsetting to think that I might have lost something wonderful because of what I said in a dream.

Dreams can't predict the future because the future isn't predetermined. You make your future.

It sounds like your dreams are a mixture of what you think and want the future with her to be like.

There is no way to know if the person she is blogging about is you. Maybe you are just noticing the things she writes about that make it sound like you, and ignoring the parts that aren't like you. This is known as "Confirmation Bias" - only noticing the things that agree with your hypothesis and ignoring the rest - is quite common.

Why don't you just speak to her and talk to her about your feelings for her and see how she feels? You have to be able to talk about your feelings with each other before you can have a relationship.