Is the continuation of a relationship with a female friend online without the father's knowledge considered disobedience?

There is no sin in conversing with a righteous girl, and there is no disobedience to the father in that, unless he forbids her friendship. The father should be informed about her, and if he forbids it, he must be obeyed, because he has a valid reason for the prohibition, due to the risks and harms often associated with these modern means [of communication].