Greetings brunow and first and foremost let your wife read most of the posts afore mentioned. As previously mentioned YOU CAN OVERCOME THIS WITH PRACTICE!
I would know because I was ONE of the WORST nose breathers my instructor ever had to train.
I could not handle any water on my nose at all. My brain just went crazy!
I got so upset that it derailed a entire pool session. I completed all the skills minus mask removal and no mask swim. I was determined to conquer my brain reflex.
I went home put my mask on and wore the thing constantly. If it fogged I knew I was breathing through my nose. I flooded it in the shower and took my shower everyday.
After a week of intense mask surface technique I went into a private pool session that I was determined to overcome it. It was not easy, I sputtered a little but I found that with practice and determination I could do it.
Actually I was more comfortable without the mask at all but I still blew air out my nose some. I have to concentrate even now not to blow air out my nose at times.
The key is to as others have said break it down into small steps and get comfortable.
It would be best to schedule a private pool session and if you attend stay away from the water or go to another area. LET HER CONQUER THIS ON HER OWN!
That is paramount in her diving future! I am not saying that you can not encourage her by all means do so. I found that it super charged my confidence and when OW came I sailed right through the skill with no issues at all.
I found that I feel much more relaxed in OW than int he pool. I have issues with chlorine, sensitivity to it actually.
DO NOT GIVE UP BUT BEAT THIS THING!
If she wants to talk to me please PM me and I will share my story with her at length.
TSandM has a great dive journal to read through as well.
If I would have given up I would have been miserable and missed out on one of the greatest changes in my life!
CamG Keep diving....Keep training....Keep learning!
That's what I'm talking about...motivation...motivation...motivation