Fear of How Breath Smells

Please help! I don't know if I have the correct area to post this. My spouse (female age 35) is deeply worried about how her breath smells. She purchases all kinds of breath products and has very, very good dental hygene. She does have sinus problems and often has a bad taste in her mouth. I truly rarely think her breath has any bad smell at all! However, she is convinced that it is so bad that it can be smelled across the room. She thinks I am just "immune" to the smell.
She has always been shy and reserved, but since this has started she fears social contact at all. It is ruining her life. She has seen doctors and specialists regarding the sinus problem. They have given her some medication to help with that but have not been able to help with any ideas regarding the smell. She does not accept that they don't notice the smell.
I am convinced that this is something to do with social anxiety instead of physical symptoms.
Any insight would be so appreciated.
Thank you so much.