themilum, I agree, the right word is crucial. I may have to coin one and I'm thinking now that "Unlover" may fill the bill. Here are the lyrics to a song (of which I don't know the particulars) that expresses the predicament in which the Lover, left by the Beloved, finds him/herself.

Unloose this hold you've got on me
You lock this heart that can't get free
Unlive the night you kissed and hugged me
Undream the dreams that we both shared
Unfeel the feelin' that you cared
Before you leave me, please unlove me
Unlove me
Unmake all the memories I can't forget
Unlove me
Let me go back to the way I was before we met
Back to the day when I was strong
When it wasn't sad to be alone
When I was happy-go-lucky
And I didn't know how good it felt
To hold you and feel my heart melt
Show me a little mercy and unlove me
Unlove me
Untie all the strings between your heart and mine
Unlove me
But do it real slow, so I don't have to lose you all at one time
Before you pack your bags and leave
One thing I wish you'd do for me
Take a little time to just unlove me
Unlove me
Unmake all the memories I can't forget
Unlove me
Let me go back to the way I was before we met
Unloose this hold you've got on me
Unlock this heart that can't get free
Before you leave me, please unlove me
Show a little mercy and unlove me


By the way, my working title is "How to Unlove Someone...in Less Than 30 Days," so this coined term may be just right, yes?