I have never solved this. Cycle kit is hard to buy for the serious female cyclist who is not in the athlete class. With different body shapes, leg lengths, pad thicknesses, waist lines, colours, sizes a shop would have to stock dozens of different shorts before I could find the perfect pair. With the number of women cycling, it's not economical for most stores to do this. She could take
@vickster's approach, and buy lots of things online.
Wiggle and many other stores have an excellent return policy with free postage, so it's easy to buy lots of things to try on then return those that don't fit.
Minx have a good range of appealing practical yet attractive clothes,
http://www.minx-girl.com/ but there return policy isn't as friendly. I've only bought a couple of things from there, but they have been great.