What is the protocol? How do we move forward when someone we loved but have lost is still around? I've seen these things turn ugly; I'm sure I've even been involved in ugly. It's hard to get to this stage in life and not have people come in and out of your life.
Continuing to ruminate about the lost friendship will only make you more depressed rather than bringing about closure. Instead, try to reframe your thinking to allow for the possibility that it had more to do with her than with you.