It’s not easy to have a crush on someone for such a long time. I admire you very much.
To be honest, it is unlikely that you two will be together. First, if you meet someone at the wrong time who doesn't know what's right or wrong, you can only say that your relationship is shallow. Love is often about fate. It's yours, as long as you don't let go, it's yours; it's not yours, even if you don't let go, it won't be yours. Don't force it! Second, the age gap. You also said that the issue of marriage seems a bit urgent for you, but as for her, she has to wait for at least a year. However, I personally think that she will get married as soon as one year after working. In this way, you have to wait at least 2 years, maybe longer. Third, she said she didn’t know you. There are two possibilities. One is that she really has no impression, but from a girl’s perspective, the probability of this situation is very low. Another possibility is that she is rejecting you in this way.
You should be more realistic if you are about to run for three years. Two people who are destined to be together will attract each other even in the vast sea of ??people. Therefore, only when you meet the right person at the right time will you be happy. It is better not to be obsessed with the past and find a new shore. Many things are illusions, such as the moon in flowers and water in the mirror. They may seem beautiful, but they have an intangible reality. Just like you said you like her, maybe you don't just like her, but you are just clinging to the ignorant and beautiful feeling at that time. Once you really get in a relationship, you may find that she is not suitable for you.
Of course, there are always exceptions. Maybe the ending will be like the prince and princess in the fairy tale, living a happy life. If you really like her, don't care about the problems you are facing now. They are all paper tigers. Try bravely and impress her with sincerity, and you will have no regrets.
Good luck!