You're being downvoted because people people think you're being obtuse, but, as a person that overuses logical thinking to a diagnosable degree, my suspicion is that you're doing that. Also because your tone is kind of...not good.

The whole point of the Serenity Prayer ("accept the things I cannot change") is that it includes "change the things I can" -- so the things Davis is changing are things she CAN change, by definition.

But her point is that she is reframing what she believes she can and cannot change. Recategorizing, if you will.

She's invoking the third part of the Serenity Prayer: the wisdom to know the difference. As we grow and learn, our wisdom increases, so the things that belong in the first two categories will shift.

Things that used to be things that can't be changed are becoming things that she can.

To understand the quote, you just have to give it some space to breathe, and not be so logical about it.