Will a girl be held accountable if she ends her relationship with a young man she met online, and he does not forgive her, while she feels guilty and fears Allah's punishment?

It is impermissible for a man and a woman who are not mahram to communicate, even if the young man is religiously committed or if the communication is for the purpose of reminding about prayer, because Satan lures the servant into sin. This relationship must be severed immediately, and one must repent. What the young man said about not forgiving is irrelevant, because he is the one who brought this upon himself. If he is sincere, he should propose to her family, for marriage extinguishes the fire of love, and "nothing is seen for two who love one another like marriage."