Is my following a girl's account on social media and directing some religious posts to her, with the intention of giving advice and guidance, considered a forbidden attachment, or is it permissible as long as it does not involve forbidden conversation or relationship?

One must thank Allah for the blessing of repentance by shunning the causes of misguidance and striving for uprightness. Among the signs of sincere repentance is to stay away from the causes of sin, for Satan lures worshippers, and Allah Almighty has warned against following 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." Whoever hovers around the unlawful is close to falling into it. Hence, Islamic law came with the principle of "blocking the means" (sadd al-dhara'i'), which is obligatory to protect religion and honor. Therefore, one must avoid following the girl's posts to avoid falling into Satan's traps.