First of all... STOP TALKING TO HER ABOUT YOUR RELATIONSHIP!
You do understand that you keep shooting yourself in the foot. You haven't worked on any of your issues yet. The clinginess, the crying, the insecurity ... that's why she's leaving.
"She's just been afraid to tell me the truth because of how I may react."
She's right.
"I don't know what to do except to call the mediator and start the process."
No you don't need to do that. Stop thinking about it.
"She has her heels dug in and will not accept any other outcome."
Yes but it can be changed. But it starts with you.
"Does anyone have any advice for me at this point? I don't know what else to do?"
I have a suggestion... start dealing with your own issues and STOP TALKING TO HER ABOUT THE RELATIONSHIP!
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.
