big hugs Jillie, that's a tough spot to be in, although I can understand somewhat. My sister had her only child (my only nephew) circ'd because her dh is.
This is ridiculous to me considering that my entire side of the family, except for her son, is intact. Granted, had my dd been a ds, I may very well have agreed to the circ., just because my dh is. Those were not the cards I have been dealt though and by the time Sam was born, both my dh and myself were (and still are) adamantly anti-circ. My sister, who is a nurse btw, told me recently that because my son is intact that his first sexual experience would be painful, I looked at her (and our mom was there too, my mother actually laughed at her for thinking such ridiculousness) and asked her if she was serious. She had no clue and even though I'm the teacher in the family, I took that opportunity to educate her misinformation. She'd never admit that she made a mistake and that it was unnecessary, but she knows that the claims of hygiene, health, etc. don't hold water with me and that I can de-bunk her desperate claims of circ. being the better way.
Oh well. Hang in there.
Intactivism is tough, especially when people refuse to take their heads out of the sand. Stand your ground, you never know if she'll ever understand or accept responsibility for her and her dh's actions.