38F - Chronic Bad Breath

My wife is a 38 year old caucasian female (US). We have been married for over 10 years. She has chronic bad breath. It doesn't matter how many times she brushes her teeth, flosses, or uses mouth wash.

She has had tonsil stones in the past, but she checks for them.

She has had chronic bad breath ever since we got married. It's BAD. I cannot be in front of her when she speaks, I cannot sleep facing her, and it's truly impacted our marriage. Mind you, I am around people all day long in VERY close proximity, so I know this is different.

She has spent years denial saying her dentist does not smell anything.. which I genuinely don't understand because of how pungent her breath is.

The only thing I can think of is that it is GERD. She's tried a multitude of things, from antacids to eating clean.. She only drinks water (no soda or alcohol).

I wanted to ask if there is anything we could possibly be missing and any treatment options or surgical routes? Perhaps a list of things to try or who to speak with.. Perhaps a gastroenterologist?

Her breath is seriously bad.. like some of the worst halitosis I've ever experienced, and it's heart breaking, because for our entire marriage I have been unable to really kiss her without holding my breath or making sure we time our breathing.. This is no way to live.

Thank you.