Their families were originally told that Marlena survived and Abby died.
On Wednesday, Guerra's parents spoke out for the first time since learning their daughter survived the July 18 crash.
Sergio Guerra, Abby's father said, "We don't want to lose her again. I feel real real bad for the other parents because they probably they are feeling the same way we felt before."
"Early Show" National Correspondent Hattie Kauffman reported even now, the two families are still looking for answers as to how such a tragic mix-up occurred.
Maria Guerra, Abby's mother, said, "I don't feel like anybody should go through this."
Extensive trauma as well as a heavy caseload in the medical examiner's office are two reasons being offered. On Tuesday officials at St. Joseph's Hospital in Phoenix issued a statement offering their prayers and support to the two families, but stopped short of apologizing.
Suzanne Pfister, vice president of External Affairs at St. Joseph's Hospital and Medical Center, said in a statement, "Clearly more details have come out about the two young women since the night of the accident but on that evening all we had to go on was the information that was provided by the families."
Now as Marlena's parents have let go of hope and prepare instead for a funeral, Abby's parents sit by her bedside hoping she'll survive.
Sergio Guerra said, "She always was a fighter, no matter what the circumstances. I'm pretty sure she will make it."
On "The Early Show" Thursday, Maria Guerra, Abby's mother, said it was painful planning a funeral for her daughter without being able to see her.
Maria said she didn't have suspicions that her daughter was still alive.
"(Hospital officials) told me -- they told me that my daughter passed away right there."
When Maria learned Abby was still alive, she said she was "so happy."
However, at the same time, she said she was scared because her injuries are so extensive.
Dorenda Cisneros, the aunt of Abby Guerra, said the family sends its deepest sympathies to Marlena Cantu's family.
Cisneros said, "Originally we did a car wash, which helped benefit Marlena for her funeral expenses. It was originally set up for Abby, for her funeral expenses. And when we found out about the mix-up, we did it and split it half and half and helped them with that as well."
Abby remains in critical condition.
"It's a day-by-day, hour-by-hour thing," Cisneros said. "And she needs all the prayer and support that she can get at this time."
For information on how you can help both the Guerra and Cantu families, please contact Wells Fargo at 602-528-7540.