Try to be gentle on the matter and talk with your wife. And she really does need to visit a doctor. That is not a big problem and it is completely treatable.
Best Wishes to you and your family)
I agree, she could have a urinary track infection or yeast infection and hygene is very important daily to avoid bacteria that can become infection. Ask her how is she feeling, because you have notice and now have become concerned of an unatural odor during intimacy and want to make sure that she is ok. If she is not feeling well or has not talked to you about her healthy, then ask if there is anything that you can do to help, such as, accompany her to her gyne. It's important for a woman to duche down there or simply soak in warm water will help, but odor is a sign of lack of hygene (bath, shower, wash) or a sign of infection. Good Luck, Judy
She could have an infection called bacterial vaginosis (BV). The usual symptom that is associated with the infection is a foul odor that is strongest when sexually aroused. I am sure that she has probably noticed it herself. Maybe approach her by saying that you love performing oral but, lately you have noticed that her odor has changed and you want to make sure she is ok. BV does require an antibiotic, but some try home remedies.