Something else to add. I think that soon you should have her using toe clips or clipless pedals. I think that having your feet come off the pedals is one of the most dangerous things about bicycles and I can't ride even cheap (riding around the block) style bicycles without at least having toe clips on them and this will be additionally important if/when you fit shorter cranks because one of the minor downsides of fitting short cranks to frames that weren't designed for them is that when you start off you now have a bigger step up to get started. I think all the benefits of shorter cranks far outweigh this one disadvantage but I would certainly want to be using a secure pedal system first.

The shorter cranks as well as allowing for a slightly higher saddle will also provide a smidgen more saddle setback at the same time.

Anthony