What is the optimal course of action for this girl who finds herself attached to her childhood friend after years of separation, and is thinking of various ways to communicate with him with the intention of marriage, taking into account her current circumstances and his age?

The most important qualities a husband should possess are religious commitment and good character. Conversations between a man and a woman who are not mahram are not permissible except out of necessity, and conversations about love and the like are not permissible. Searching for someone's account on Facebook and looking at their picture is a door to temptation, and you must repent from that. If the matter requires years to complete the marriage, it is not advisable to wait; rather, look for someone else, for men are many. If you find a man whose religious commitment and character are pleasing, accept him and do not regret missing out on marriage to the first. Entrust your affair to Allah.