Filing while she is unmarried and under twenty-one does not by itself guarantee derivative eligibility. Her Child Status Protection Act age is generally calculated when a visa becomes available by subtracting the petition's pending time from her biological age, and she normally must seek to acquire residence within one year.
File while she is nineteen; let the statute hold her age
EB-5 derivatives are the investor's spouse and unmarried children under twenty-one. A child's CSPA age is generally the child's biological age when an immigrant visa becomes available minus the time the petition was pending, subject to the requirement to seek to acquire residence within one year. A daughter who is nineteen at filing is therefore not automatically protected through every later delay.
Visa availability must be checked in the current bulletin for the applicable category and country of chargeability rather than assumed from Canadian residence or nationality. Marriage ends derivative eligibility regardless of age. The practical advice is to file as early as the source-and-path record allows and calculate the daughter's position from the actual dates.