Brian, has she specifically excluded you? Maybe she thinks you would be bored. Why don't you just GO?
I also belong to a ladies group that I formed about 13 years ago. Most of the time it is just women but every now and then a husband will come along. A time or two my husband came, and when he died these were the women who rallied round me. Now my bf will go occasionally, but honestly, all of us are in the fund raising business and the talk is usually pretty boring for someone who isn't in our business. I've invited my bf and told him don't feel obligated.