Adding hair is really a very easy thing to do. The most important part is having enough good images of the model’s hair in the same lighting. So, don’t hesitate to take more than needed in a case of hair flips like this. That way you can blend more than one together.
Side note on hair flips. Yes, you can use a fan to make hair fly but it tends to make the hair go wild in ways you don’t want. It dries out the model’s eyes, and actually, her head is in the way for the fan to work on the hair well.
Try just having the model put hair forward on both sides of her shoulders and use a foam board to flip a puff of air that will blow the hair once and make it fly up on both sides and it will tend to drift up into beautiful high arcs. I’ll do a video session showing how that works soon.