Well I like unrequited love since it seems to be love par excellence. It also seems like the virtue of magnanimity in that it gives you practice in sacrificing a lot for very little.
Then why did you write to ask for advice or help to anyone who might respond if you are happy with your condition?
All love is trinitarian. There is a lover, the beloved and the love itself. God is love. Love can not exist by itself. There are The Three Divine Persons. The Father gives Himself entirely to the Son and the Son returns to the Father.
Apart from thoughts about whether or not there can be such a thing as unrequited love it seems you need to ask yourself some questions. This has been going on for quite awhile. How long, how much of the rest of your life do you want to remain with this romantic attachment that is in your mind? Would it be ok if you stay this way for the rest of your life?
You said this woman showed you some kindness and therefore that created this romantic feeling or notion you have not been able to let go of since. You question if there is something disordered there so you must wonder yourself about what you are experiencing.
It is fairly normal to be appreciateive of a kindness. It is kind of strange that this would trigger a long term response of feeling a romantic attachment to a person from a distance. You did not say what this kindness was, but you must have perceived it as a very significant event in your life, very important, given the response.
Are other relationships in your life successful? Would you say you have normal friendships, people you like and with whom you share time and interests? Are you more introverted than extroverted?
Would you prefer getting over this attachment that seems to have no future and move on with life, or would you rather cling to it? Does this attachment make you happy, or does it hurt?
It is often difficult for everyone to understand why we do what we do. Often people do things that make no sense, but they feel compelled to do them and can not explain why.
We are made to love and be loved. Some of us find it and some do not. If you like the situation you are in, unrequited love, then stay there. You do not need help from strangers on a forum to accomplish this. God bless you on your journey.