If she has her birth certificate back in Libya, get somebody to mail/bring it over. If she never had it, or it was lost, etc.:
http://uscis.gov/graphics/formsfee/forms/files/i-130.pdf
from form I-130:
What If a Document Is Not Available?
In such situation, submit a statement from the appropriate
civil authority certifying that the document or documents are
not available. You must also submit secondary evidence,
including:
A. Church record: A copy of a document bearing the seal
of the church, showing the baptism, dedication or
comparable rite occurred within two months after birth,
and showing the date and place of the child's birth,
date of the religious ceremony and the names of the
child's parents.
B. School record: A letter from the authority (preferably
the first school attended) showing the date of admission
to the school, the child's date of birth or age at that time,
place of birth, and names of the parents.
C. Census record: State or Federal census record showing
the names, place of birth, date of birth or the age of the
person listed.
D. Affidavits: Written statements sworn to or affirmed by
two persons who were living at the time and who have
personal knowledge of the event you are trying to prove.
For example, the date and place of birth, marriage or death.
The person making the affidavit does not have to be a
U.S. citizen. Each affidavit should contain the following
information regarding the person making the affidavit: his
or her full name, address, date and place of birth and his
or her relationship to you, if any, full information
concerning the event, and complete details explaining
how the person acquired knowledge of the event.
