Must I apologize to the girls online against whom I have transgressed, for Allah to accept my repentance?

A man's conversation with a non-mahram woman without need and without observing the Sharia regulations is forbidden and a door to temptation. Your mere conversation with them does not create an attachment to their rights or an offense from you against them. Repentance between you and your Lord is sufficient for you. Do not pay attention to the whispers of Satan, which may be a ploy from him to lead you back to temptation, for Allah has warned against his footsteps: "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." We advise you to strive for righteousness and to beware of the causes of temptation.