Messick, 50, who was battling from depression for years and was recently diagnosed with bipolar disorder, committed suicide in Los Angeles, her family had said in a statement.
"For Jill: May your family find some measure of solace during this pain. That one man could cause so much damage is astounding, but tragically true.
"The bad man did this to us both. May you find peace on the astral plane. May you find serenity with the stars," she wrote alongside a photo of the sun behind the earth viewed from space.
Messick served as McGowan's manager in 1997, the same year when the "Charmed" actor alleged rape by Weinstein. She later served as a production executive at Miramax, a company owned by Harvey and his brother Bob Weinstein, from 1997 to 2003.
In the aftermath of multiple exposes that revealed the extent of Weinstein's sexual transgressions, McGowan went public with her own account.
She had claimed that ex-manager arranged the meeting with Weinstein, which took place in a hotel room.
Messick's family said the whole saga had a devastating effect on her as she was already battling depression.
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