Prominent Rear End and Altering the Crotch Line

I measured my daughter with a tape measure that has been modified so that it has a center that starts with zero and reads out from the center.  The middle of the tape has a string and weight so that you can determine where the crotch and seam lines fall. 

From the center of her crotch to her back waistline measures 22".  From center to her fron waistline measures 15", for a total of 37".  Measuring the front crotch with the tape on the side and walking it around, it measures 33.8 cm or 13 5/16".  Measuring the back crotch it measures 44.8 cm or 17 5/8".

What I want to know is do I split the number and add some to the crotch extension and cut the pattern top (per your video) and add the other half measurement (on each pattern piece)?  Or do I cut the top and add it all at the point in the pattern?

Thanks for your help and I think your site is the very best.  Your videos are professional and the fact that you can pause them and work along with the instruction is awesome.  I also like the slow pace of the voice and how the chapters are broken up.