First, I am sorry about your recent loss. You are absolutely correct on both statements, first that the virus could have lain dormant in either you or your wife for many years, and secondly that stress can certainly adversely affect your immune system to the point that you could have a new outbreak related to a virus you were exposed to years ago.
HPV (or Human Papillomavirus) is very common, affecting about 60-80% of us at some point in our life. It is the most common STD in the United States. There are several dozen types of HPV, some of which cause cervical cancer, and others which can cause cancers of the cervix, throat, or anus. Most people who are infected with HPV do not have any signs or symptoms, and will never develop any problems associated with the HPV.
For some, however, depending on which HPV they've been infected with, they can develop abnormalities of the cervix (which is why we check pap smears) or genital warts. The virus can remain dormant within your body for years. Again, for most people, the virus will never outwardly manifest or affect them in any way, but for some they can develop abnormalities of the organs mentioned above, or genital warts. Stress, how much you're sleeping, what you're eating, etc can all negatively affect your immune system, even to the point where you can develop a first-time outbreak of genital warts.
There are several treatment options for warts including Trichloroacetic acid treatment to the warts at the doctor's office, cryotherapy at the doctor's office, or a cream that you can apply yourself. Sometimes small warts will come and go on their own. In general, even though you are both almost certainly infected with HPV, I do not recommend intercourse while you actively have warts, just to minimize the risk of passing along an active infection. Your wife just needs to make sure she gets her exams and pap smears on schedule. (The type of HPV that causes genital warts is different from the type that causes cervical abnormalities that can lead to cancer and it would be rare to be affected by both types of HPV, but I recommend staying on schedule with paps to all women in general anyway.)
Again, I am sorry for your loss. Self-care is still important and please try to make sure you're getting enough sleep, rest, and eating well. The CDC has more info about warts and treatment here.
On a tangential note, I in general also recommend the HPV vaccine (Gardasil). It protects against 4 different types of HPV, 2 of which cause warts and 2 of which are related to cancer. Women can receive the vaccine up to age 26 (even if they have been exposed to or tested positive for HPV in the past) and men can receive it up to age 21.
Good luck to you both. Please leave a rating if you feel so inclined.