I would love your feedback. 

Thank you so much for taking time to share your experience with me. Testimonials help others when deciding to work with me, so this means so much you are doing this.  

xoxo Kimberly

You can simply write a few sentences regarding the help I provided or the difference I made.  Anything about your experience is so appreciated. (And, if you see any opportunity for improvement or anything else you would like to share, I'm all ears.)