Is it permissible for a Muslim girl and a Muslim young man to exchange words of love via social media despite the distance?

It is not permissible for a girl and a non-mahram (definition) man to exchange expressions of love and flirtation, whether he is Muslim or non-Muslim, a relative or distant; because it is a gateway to temptation. Allah Almighty said: "O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan - indeed, he enjoins immorality and wrongdoing." Marriage is the best solution for those who love each other; so if marriage is possible, then all the better, otherwise, each should go their separate way. Attachment and infatuation can be treated.