"Do you use hair that is just for
the Girl?"

No.

Any hair can be made to fit just by scaling and moving it around with the dials.
(If the hair is a character instead of a prop, don´t conform it, but parent it to the head of your figure. Then move and scale the hair´s body.)
If scaling and moving doesn´t suffice, use magnets.
Usually one or two magnets are enough to make even the most stubborn hair fit.
Convert the mags into a morph target and save the modified hair to your hair or character library so that you can use it again.

Stahlratte