I actually agree with you, I think she was definitely horrified that she voted for it, too. But I also didn't get the sense that she felt guilty for it, if that makes any sense? She points out twice that she doesn't remember, like she's using it to say "and therefore how can I be responsible?" and her "I'm... I'm sorry" sounds a bit like "I know I'm supposed to say this now." (I admit this may totally be a YMMV reading though!)