Personally, I dont think its anyones business. Why do they need to know. I too would just say 'she couldnt make it today'.
I remember when my mother told all our friends and relatives about my sister being an 'alcoholic' it created such a load of gossiping b.s. and they all felt sorry for my mother, not my sister. Telling them actually created a nightmare because it gave my sister the licence to ring them all up and tell them what she thought of them. (when she was intoxicated of course). It went from embarassment for my sister to 'you are all against me, so Ill give it back to you'.
JJ