It's not clear whether your daughter is using TurboTax.
When she amends her tax return, she must recalculate the return based on being able to be claimed as a dependent. If she is using TurboTax, she does this by following the instructions that xmasbaby0 gave above.
In addition, in Part II on page 2 of Form 1040-X there is a box to enter an "Explanation of Changes." She should write in there that she is changing her return to say that someone can claim her as a dependent. If she is using TurboTax, when she amends her return she will come to a screen that asks for a description of why she needed to amend her return. What she enters on that screen will go in the Explanation of Changes in Part II of the 1040-X.
