I've not been doing this for very long, so I'm sure others would know better; but if the holster is just for range work, I would think a straight drop should be fine. I was under the impression that the FBI cant was for concealment purposes. So, if this is just for range work, it shouldn't matter.
Personally, under good advice, I got a Blade-Tech DOH to use for range work and IDPA. It wouldn't work for me for concealment, but I'm not "there" yet anyway.
Have you ASKED her what she wants?