Here’s a quick tutorial on how to select and refine edges around hair when making selections in Photoshop
Begin with the Quick Selection Tool and select the central areas that are easiest to grab first. When selecting the hair, the tool will probably select areas of the background.
Deselect the area of the background by holding down alt/opt key as you paint with the Quick Selection Tool. You can adjust the size of the brush tip by using the bracket keys.
Press the Refine Edge button and in the dialogue box increase the Radius until most of the background around her hair disappears. Then reduce the Shift Edge slightly and increase the Feather a bit.
Now click the Refine Radius Tool, it’s the little paint brush icon along the left side of the window. Use that to paint over the white areas in her hair and further tighten the selection.