I would take your daughter to see your pediatrician
at your earliest convenience to have this issue checked out.
I assume that your daughter is not bothered by this clicking, that is, that there is no pain, stiffness, or trouble moving the neck, nor any recent history of a fall or trauma to the area. If this is not the case, then I would prioritize evaluation much more quickly, as the clicking sound may be related to a more serious problem in the neck.
However, in the absence of these symptoms or history, the clicking sound is much more likely due to normal elasticity in the ligaments around the bones of the spine, which can sometimes make a "snapping" sound, or to the production of small air bubbles in the spinal fluid (analogous to the sound that occurs when you crack your knuckles).
Nevertheless, your pediatrician will be able to perform a thorough examination, looking for any evidence of spinal misalignment or other issue that might require additional workup, such as X-rays of the spine, or referral to a specialist, such as a pediatric orthopedic doctor
Please make an appointment with your daughter's pediatrician at your earliest convenience!