Your on the right track and if you are not working with an assistant, many times your only choice is to utilize natural reflectors. The key to using reflector fill is making sure you are getting light into the subjects eyes. If you are not creating a catch light the subject seems lifeless. With your model wearing dark glasses it's hard to say if you would have achieved this goal or not. Do you have any other images without the shades? She is a lovely girl.
Re: Midday sun.