I need advice,

I have a female friend that I e-mail. My DW knows about it but, she is not comfortable with it. After much discussion and lots of loud words and accusations she wants me to end it and to be honest I would like to end it too. My DW has called this woman twice over the past 2 years and asked her what she wants with me. We are friends....she tells me her problems with her husband, I have never let her know anything about my relationship with my DW. In recent days she has made some very derogatory comments about my DW and I feel they are inappropriate. I wanted to answer her last e-mail and say I don't want to be in contact with her anymore. How would you end this situation? I don't want hurt feelings, yet I don't want to stay in this friendship. I am really upset over what this friend said about my DW. I have never made any nasty comments about her DH, what is this and why? Anyone have any insight?

I'm at a loss for how to handle it.