No she cannot. She will have to contact the county or state records bureau and obtain a certified copy with the official seal. If she is cruising soon she will need to do it as soon as possible.
This is what Carnival required for proper identification:
"(c) Proper travel documentation is required at embarkation and throughout the cruise. Any guest traveling without proper documentation will not be allowed to board the vessel and no refund of the cruise fare will be issued. United States citizens must produce proof of citizenship in the form of a passport (valid or expired for less than 10 years), original birth certificate, state-issued certified copy of birth certificate, U.S. Military ID, or original Naturalization papers."