The only thing I can think of is perhaps she has some kind of "moral issue" with premarital sex (which, rather obviously Kaylee has engaged in), but since this isn't the Victorian Era nor a Nathanial Hawthorne novel (well, he was actually criticizing the arbitrary discrimination of illegitimate children, in a way) - ...I don't know. That seems both petty and childish. And then the moral issues regarding your own situation come into play - an island of genetic experimentation can hardly be said to be on higher ethical ground than premarital sex. So perhaps it's a reaction to that.