Wedding Invitations

Recently, I showed my soon-to-be mother in-law our wedding invitations. Not only did she not say that she liked them, but she also said how offended she was that their, groom’s parents, names were not on the invite. Surprised, no shocked, I couldn`t believe this. My parents were the ones paying for the wedding. Do they have a right to be hurt by this? Should I have included them as a sign of respect? (These are very traditional invites)