How do I stop my neighbor’s AirTag from pairing to my iPhone?

Hello neelab144, This Apple Support page on AirTags might help you. Scroll down to the section that says;

"Get information about or disable an AirTag, Find My network accessory, or set of AirPods"

What to do if you get an alert that an AirTag, Find My network accessory, or set of AirPods is with you - Apple Support

They aren't pairing to your phone at all. They are just sufficiently nearby as to trigger that warning if the owner of them is not near them too.

There's nothing you need or can do other than walk away from them or tell your neighbor to not leave them laying around near you.

Its warning you that they are nearby, not pairing with your device in any way.

Seems like her devices are sufficiently close by to your iPhone that it triggers the warning when your neighbor is not around, i.e has left the devices alone and separated from the paired iPhone. It should not trigger, when she's around since her iPhone would pick up her devices and not cause the notification for you.

Other than you moving away from the devices enough so your iPhone cannot detect them, there's not much that can be done.

The message indicates there's an AirTag around 30 feet from your iPhone that is not near its paired iPhone.

Go to the Find My app, tap the Me tab, and turn Tracking Notifications off. See if that helps.

Note that this will turn ALL tracking notifications off, desired or not.