I guess we both do. We're on the same cell phone account...family plan...and it's paid out of our joint checking account. Just happens to be under her name since we used her employer's discount.
Do you think it's right to use your family's funds on a phone that she uses to conduct her affair?
I suggest you cut hers off, and let her know why you did ("I will no longer use our family's money to help finance your afffair.")
It's enabling. Are there any other ways she is squandering marital assets? Gifts for OM? Clothing? Jewelry? Cosmetic surgery? Other? (EDITED to a add: Dinner @ romantic restaurant??)