Deborah Duffy, 54, who previously worked for WG Trading in Connecticut, admitted illegally transferring over $100 million to the company's partners, Paul Greenwood and Stephen Walsh.
The pair had been arrested in February on suspicion of running a fraud scam for a decade, in which they used clients' money for their own personal gain.
Duffy, who was charged with conspiracy to commit securities fraud and wire fraud, securities fraud and money laundering, told the court that her actions "caused investors to receive false information, which I knew was against the law," Reuters reports.
She is due to be sentenced in January of next year and could face up to 20 years in prison.
In related news, Morgan Stanley has agreed to pay the Securities and Exchange Commission a $500,000 settlement in relation to charges of misleading its customers.