How do I ISOLATE MY HOUSE FROM THE RESIDUE FUMES OF OTHER PEOPLES AIR FRESHENERS

Have you politely In a note explained the problem to your neighbours and requested they not use these particular air freshners? EDIT i can see that you have.

I would try to track down If you can which brand or brands your partner is sensitive to and mention these in your letter to your neighbours.
Ambi-per plug in is one that my wife found distressing. Some of the supposed car air freshners are also more than annoying to her.
Keep a copy of your letter for reference. Make sure it is dated. perhaps a copy of a medical report could be included.

How does your tennancy work? do both you and the neighbour rent from the same owner? Is it strata title? perhaps theres an avenue there.

Not sure where you live, but if the neighbour has denied using them, maybe the problem is with the vents and dust build up, perhaps they need cleaned. Other than that, perhaps you could get a portable air scrubber.

i was going to suggest something along the same lines. If it is not coming from the people you share a wall with, it is highly probable that it is coming from the shared venting system.

If you are living in an apartment building, you can get a letter from your doctor explaining the issue and have the property owner clean ALL of the vents in ALL of the complex.
You will NEED to leave for that though. Be prepared to stay some where else for about a week to let that dust and debris settle.
That should help a lot.

And as dadpad said, it could just be a specific brand too.
But do know that the ingredients IN those plug ins can also be found in scented cleaners too. They may not be using air freshener, but their fragranced floor soaps might be adding to the issue..