And when the guilt was eating at Jax and he wanted to give up the lie and give the baby to Nikolas, CARLY was the one pressing him to keep the lie going, that they had every right to keep the baby from Nikolas.
That's why she gets credit as a partner, for her actions once she learned the truth. She instantly became a partner in crime and actually wanted desperately to keep it going.
And while Jax was evil for stealing the baby, he at least felt GUILTY about it and confessed to it.
Carly never felt guilty at all.