Heng organised 13 electronic fund transfers from Legacy's bank account to the bank account of Regency Infrastructure, a company she controlled, between June 28 2012 and November 6 2013.
According to the Australian Securities and Investments Commission she concealed the transfers from the Legacy board and used the transferred funds for her own benefit.
The mater has been committed to the District Court for a sentence mention on September 23.
The maximum penalty for the charge Heng is facing is 10 years imprisonment.
The Commonwealth Director of Public Prosecutions is prosecuting the matter following a referral from ASIC.
Heng was the founding director of Legacy and from April 20 2007 to October 31 2014 she was its managing director.
According to its latest quarterly report, Legacy has "10 promising projects encompassing 22 tenements in the Western Australian known mineralised belts".
Heng is not the only one involved in the case.
Former Legacy bookkeeper Karen Kwan has also been charged with stealing in this matter.
Her hearing has been adjourned until August 26 at the Perth Magistrate's Court.