In the worst possible scenario, which frequently happens, the girl, in an effort to improve her “self image,” may turn to various other habits such as smoking, clubbing, drinking and drugs, or she may embark on a series of flings just to make herself feel “special” again.
Regarding fornication, Allah Ta’ala says in the Holy Qur’aan: “The woman and man guilty of adultery of fornication, flog each of them with a hundred stripes: let not compassion move you in their case, in a matter prescribed by Allah, if ye believe in Allah and the Last Day: And let a party of the Believers witness their punishment.” [Surah An-Nur: 2] How can there be any long term happiness in a sin for which the punishment prescribed is so severe?
In real life, such relationships lead to nothing but unhappiness and heartache.
For how can there be any real happiness in a “love” inspired by Shaitaan?
It is usually exactly the opposite: she wishes she was the person on the pages of the book, and transfers her fantasies to her real life.
She might see someone at school, who is popular, and good-looking [i.e.