I have noticed that women at my shul don’t wash Mayim Acharonim after Saturday Kiddush. I was asked if this is simply not an obligation for women or if there is a prohibition against their doing so. Is it inappropriate for women to wash Mayim Acharonim when a minyan is present?

One should always be careful of learning Halacha from what people do or don't do. The Halachic obligation of Mayim Achronim nowadays is not definite; the initial reason of Melach Sedomit may not apply today. If the hands are dirty they should be washed before Birkat Hamazon. There should be no difference between men and women regarding the above Halacha, some people are stringent and wash, others follow the practice not to. (Shulchan Aruch OC 181:10 and Mishna Brurah ibid.) The Kabalistic custom is to wash.