Rape is rarely prosecuted under Sharia because of the need for eye witnesses. Sometimes in a situation like this, if she becomes pregnant, the young woman will be tried for fornication and punished instead of the rapists.
Here we go again... Please get your facts right...
What you seem to be referring to up there is Zina, whilst rape would be classified as Zina Ul Jabr: the issue of Zina and Zina Ul Jabr were covered under an archaic law called the Hudood Ordinance:Under Pakistani Statute here is the correct explanation of Zina Ul Jabr:
A person is said to commit zina-bil-jabr if he or she has sexual intercourse with a woman or man, as the case may be, to whom he or she is not validly married, in any of the following circumstances, namely:--
(a) against the will of the victim,
(b) without the consent of the victim,
(c) with the consent of the victim, when the consent has been obtained by putting the victim in fear of death or of hurt, or
(d) with the consent of the victim, when the offender knows that the offender is not validly married to the victim and that the consent is given because the victim believes that the offender is another person to whom the victim is or believes herself or himself to be validly married.
Explanation.--Penetration is sufficient to constitute the sexual intercourse necessary to the offence of zina-bil-jabr.
This understanding comes from the now obsolete and repelled laws of Hudood: he "Offence of Zina (Enforcement of Hudood) Ordinance, VII of 1979.
In Modern Day Pakistan we replaced the Hudood Ordinance with the "Protection of Women (Criminal Laws Amendment) Act, 2006".
Under the Protection of Women (Criminal Laws Amendment) Act, 2006, Rape is defined as:-
"375. Rape:-
A man is said to commit rape who has sexual intercourse with a woman under circumstances falling under any of the five following descriptions,
(i) against her will.
(ii) without her consent
(iii) with her consent, when the consent has been obtained by putting her in fear of death or of hurt,
(iv) with her consent, when the man knows that he is not married to her and that the consent is given because she believes that the man is another person to whom she is or believes herself to be married; or
(v) With or without her consent when she is under sixteen years of age.
Explanation: Penetration is sufficient to constitute the sexual intercourse necessary to the offence of rape.
And the Punishment for rape in Pakistan under the said law is:
376. Punishment for rape
(1) Whoever commits rape shall be punished with death or imprisonment of either description for a term which shall not be less than ten rears or more, than twenty-five years and shall also be liable to fine.
(2) When rape is committed by two or more persons in furtherance of common intention of all, each of such persons shall be punished with death or imprisonment for life.".