Communication is important even if it's a subject you don't like discussing. She has to understand it is not her you are rejecting. Feeling rejected can affect her self-esteem. This is going to be a barrier between the two of you until you can talk about it and come to some sort of compromise. It's not fair to refuse to talk about it. Seeking therapy would be a good idea. I hope the two of you can work this out, sex is a big part of marriage. I'm sure she feels hurt and rejected. Not a good situation for a good marriage. Hope you get help.