This is something I remember hearing in a talk then later from an Elder I respected, it lead me to confess a sin I had been covering up.
Prov. 28:13 "He that is covering over his transgressions will not succeed, but he that is confessing and leaving [them] will be shown mercy."
Luke 8:17 "For there is nothing hidden that will not become manifest, neither anything carefully concealed that will never become known and never come into the open.
Luke 12:2 "But there is nothing carefully concealed that will not be revealed and secret that will not become known."
The reason I was so bothered by my past sin was that it seemed no matter how much I prayed, no matter how much I went out in service, to meetings, studied ie; acted in harmony with my prayers my family was still sufferning and in a week spiritual state. I was doing my very best and when I heard this scripture from a talk one Sunday morning a light bulb went off and I felt compeled to confess my sins thinking I was the one holding back Jah's spirit from our family.
Nothing really changed, I just felt better. Later I found out (way later) my husband had MANY sins of serious concern he was covering up.......hummm maybe I wasn't the weakest link after all.
So maybe you could go to the Elders and talk to them or just reason with you wife with the scriptures I mentioned? Eh, it worked for me, played on my guilty conscience enough maybe it will work for her and she'll do her own confessing.
Best of luck however it turns out.