The parameters outlined from @DoninGA and @LinaJ2020 explain the IRS rules for who is a dependent. In the eyes of the IRS, the determination is not that she could have supported herself, but that she surpassed a threshold where she can no longer be claimed as a dependent.
To verify the information, run through the Interactive Tax Assistant, go to Whom May I Claim as a Dependent? | Internal Revenue Service
@rgomez92
