The ‘overdeveloped’ view could be how your client views his (or her) calves.
As Harris and Christine said it could be genetics (unfortunately that is not in your control).
There’s no need to place heavy emphasis on calves (other areas can receive more attention) but you can use Karin’s idea about the calves.
One area is important: if her calves receive a lot of attention what about the tibialis anterior (is the muscle that opposes the calves ‘overdeveloped’)?
Everyone pretty much covered it. They shouldn’t be neglected and light work will be more than fine. I’m sure it boils down to genetics. I had a friend who was really skinny but had huge (perfectly sculpted) calves that a bodybuilder would die for. His father was built exactly the same way. In my family it’s back and shoulders in another friend’s family it biceps and forearms.
Coach John Kane CPT