There are many reasons women may have pain with sex, so I can’t be certain of the specific cause for your wife. A pelvic examination by her health care provider is needed to determine the cause and therefore the proper treatment.
That being said, the most common cause of painful intercourse in perimenopause (the phase before menopause) or post-menopause (beyond the year after the last menstrual period that marks menopause) is due to the reduction or loss of estrogen and the atrophy or dryness that result.
Using a vaginal moisturizer regularly, two to three times a week, is a great place to start; if the atrophy is not advanced, restoring moisture to the tissues may help. Using a silicone lubricant with sex may help, too. I recommend Pink, which is very slippery and, because it has Vitamin E and aloe, it’s soothing, too. If there’s been some vaginal narrowing in the process of atrophy, vaginal dilators can be helpful, too, by gently stretching the vaginal tissues.
I hope this is helpful, and encourage you and your wife to pursue a medical evaluation to enhance her chances of regaining comfort! There may be a physical issue that needs addressing, and there are also prescription-only products available to address her symptoms. For a practitioner focusing on menopause care, I recommend the North American Menopause Society’s practitioner finder.