By default, codes are not sent to a cellular telephone number. That number is for backup contact. The default means of sending codes is to send codes via iCloud encrypted notifications to all trusted devices. Since the trusted devices are determined by the AppleID logged into the device, there is no way for you to receive codes for someone else’s AppleID. The whole system would be pointless if that were even possible.
So the codes will come to her trusted device(s) - those devices signed into iCloud with her AppleID. There is no way to change that default system for 2FA codes. The system is based around that concept of trusted devices and telephone numbers are only usable as backup contacts in the event a trusted device is not available. Trusted telephone numbers would be the ones your daughter has entered into her online AppleID information.
iCloud encrypted notifications are considered far more secure than SMS texts, which is why the default code system is set up that way.