Even at the beginning of their relationship, in an interview, she said something to the effect that she "anticipated she would enjoy his company for a time." Not forever, not even long-term, just "for a time." Which could have been 13 months... or 30 seconds!
Meanwhile Andy was dreaming of marriage and children and "Everlasting Love" with this woman. I think that may be another reason his family was disgusted with her. They probably knew she was Just Not That Into Him.