OK, to answer your Question - there is nothing illegal about what you propose to do, but there is very much that it wrong with it.
I have three daughters, two are older than the woman (and accept that this is what she is) in this sad story. I accept that my daughters are all grown women, they have partners and children, and I have brought them up to respect themelves and other people.
If someone rang me out of the blue and told me my daughter was having an affair, I would be very hurt and disappointed - and as an innocent party, I would question the caller's motives. My relationship with my daughter would be damaged - even though as an adult, her behaviour is her business, and that would be unfair on myself, my wife, and my family.
Regardless of how we raise our children, as adults they do as they wish - and that includes this woman, your husband, and indeed yoursrelf. Put yourself in the parents' position and think what is really to be gained by hurting them when they have done nothing wrong.
You are very hurt and angry, you want to hit back and have some revenge for the hurt you have been caused. An innoncent person hurting other innocent people can do no good at all. Your anger and revenge (if you wish) belong with your husband, and no-one else.
You will regret this action if you take it. Please think very hard before you do anything.