Australian star and the Russian songwriter were involved in a heated custody battle over their young daughter Lucia in 2011, and Grigorieva won $US750,000 ($A835,514) from the settlement, which is to be paid in instalments until 2016.
But three years later, her funds have dissipated, and Grigorieva has filed for bankruptcy, according to TMZ.com.
In legal documents obtained by the news site, she has declared $US48,000 in assets, but $US438,000 in debts.
Grigorieva claims she is owed money for song royalties as well as paintings she's created.
And while her incoming funds include Gibson's $US20,000 a month in child support, as well as $US2500 from actor Timothy Dalton, with whom she has a son, it is not enough to cover her debt.
In the documents, Grigorieva states that most of her debt stems from the legal fees she ran up during her custody battle against Gibson. She was initially offered a $US15 million settlement from Gibson in 2010, but she refused it.
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