This is a non-problem, blown up out of all proportion.
Spiritual healing is something you are either into or you aren't, but your husband's interests are not something that you should be ashamed of have to be ashamed. Is he good at it? Why should he be ashamed of it, and if he isn't, why on earth should you be? What he tells his friend about himself is his own business. How can he even carry it out without telling anyone about it, anyway? He would never have contact with people who needed him
If your cousin returns to her old ways, just tell her to get lost and that your loyalty is to your husband, so you don't care what she thinks. But it isn't, is it? Your main thought is whether people will think you are somehow odd. You are being Hyacinth Bucket.