No, the way you feel is perfectly reasonable. As to whether you tell her or not depends on how much you consider her children and animals to be at risk. You could explain it to her, but then if you're not prepared to stick around and offer any help to rectify the situation, this seems a bit unnecessarily mean. But then there's no reason for you to want to stick around, it's not your problem. Ask yourself if all was well, would you still want to be friends? On the other hand, even if you don't want to stick around, do you really think that she's putting her kids at serious risk? Try and be objective - we don't all have the same standards and idea of what is clean/hygienic. If you do tell her, I'd just try to do it in the most positive way you possibly can. She must know her situation isn't ideal - maybe she's feeling down about it and doesn't know how to start improving her home. You have been friends for quite some time, it seems a shame to part under these circumstances, but you have your own family to think of. : )