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I would talk to her and let her know that you are hurt from what happend. That you understand that she made a choice to move on but you do not feel it is apprpriate to live above her aymore since it brings up hurt in you. Ask her if you could move to another apartment in the same complex where you would not see her so often and defiantly would not hear her or if she can move. It is going to be hard to "move on" as long as she lives under you.
I hope this helps. Please let me know if I can assist any further. I am here to help.
Thank You...This is sort of a 'Reality Bites' Q ? - I know.