<human>: Can you provide a brief rundown of the text in within 3 sentences?

My fiance told me, this past Thursday night, that his dad, who is a white collar criminal (creative accounting), and sociopath that he should "trade up" and dump me, and get with my sister. I am 37, she is 34.  Why would he tell me this?  I am so upset. My mom was always second place in my father's heart (now deceased, thank God), I was even named after her, my dad's love "Melanie".  I have always gotten inklings of it, growing up, with my grandmother always telling Dad that he should have gotten with her, in my mother's presence.
<bot>: My father in law to be told my fiancé to dump me for my sister. I'm angry that he even told me.