Trouble having Contacts and Messages syncing across multiple devices

See these threads iCloud contacts not synching to Macbook A… - Apple Community

Merge primary email across all devices - Apple Community

Your MacBook should be definitely upgraded to sync the data macOS - How to Upgrade - Apple

Your wife device should be signed in with same Apple ID and password with other devices ( Mac , iPhone , iPad ...) on the same network , you can't use different Apple ID signed in on her device to sync the data .

messages will also sync , when you set up iCloud messages on all devices Set up iCloud for Messages on all your devices - Apple Support

Am in a similar situation with Calendar not syncing. All respective devices are updated to current OS with same iCloud account signed in across all. What worked was opening the calendar app on the MacBook Pro (sequoia macOS 15.3.2), and under Settings > Alerts > Accounts: On my Mac

1) adding in default times to events and

2) checking box for “show shared calendar messages in notification center”.

Calendar is now sinking across all devices, whereas before Events added on the Mac weren’t syncing with the other devices. Double checked Messages on the Mac and under Settings, ensured “Enable messages in iCloud” was checked and selected “Sync Now”.