Many women do not want to be watched by their husbands. Of the several hotwives I have had over the years only one wanted her husband to watch, and that was just a one off after I had been talking to them for about a year. I think they were just checking it out.
My first hotwife used to like to us to both meet her husband for brunch the morning after she spent the night. She made sure to have a fresh morning load in her before we went to meet him. I expect they played after brunch.
Others hotwives have had me speak to their husbands before and after we were done, but the majority I have been with simply told their husband they were going out with their friend and left it at that.
If she does not want him to watch then he just needs to get over it. She may be feeling guilty about it, and begging to watch is not going to help. He should work on being close to her, loving and supportive in non-sexual ways, and maybe suggest to her that she let him practice his oral skills on her on a regular basis.