Should I leave her with the truth or not?

After my best friend and love of 7 years died, I was just gonna end it too. Then as a last ditch effort to find happiness and a reason to live, I started dating a girl to see if she could unknowingly "save me", so to speak.
Now I realize that wasn't her responsibility, and to be honest, it's not working. My heart is gone. I've got some things left to do, then it's time for me to go.
Is it best to leave her with the truth, or just end things with her on a vague note?
I won't stay with her and make her suffer the same loss I did. I know what that feels like
Should I leave her with the truth or not?
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