An update:
Somehow, probably with the advice given by posters here, I managed to get up enough courage and I sent a note to the woman I referenced in my first post to this topic. Here's what I sent just a few minutes ago:
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Hello <friend's-first-name>:
This is your old friend <my-name> back from your days at <college-name>. I hope that everything has been going well for you and that you might remember me from the times we spent together. I don't know if you will believe it, but I think about you quite a lot and I often mention you to my friends when they ask me about the important people in my life from back in college.
Mostly what I want to write is that it wasn't until years after I last saw you that I had enough experience with relationships to fully understand how wonderful and special you are.
If you would, could you reply and let me know how you are doing, because I'd really like to hear from you.
Always Proud To Be Your Friend,
-- <my-first-name>
<my-e-mail>
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So, women readers, do you think she will reply?