The best situation is to use the type of faucet made specifically for this application where there may be freezing exterior temperatures. The faucet is an assembly that has an almost standard looking external spigot but the valve handle connects to a shaft inside a long pipe on the back end of the assembly that sticks in through the wall. The shaft operates an internal valve that projects a foot or so inside the wall to where the temperature is certain to not fall below freezing.
Typical installation detail:
Proper installation and usage in freezing weather requires that the portion of the faucet assembly with the shaft within be tilted downward toward the spigot end to permit that portion to drain out when the faucet is off. Obviously the hose should be removed as well.
You have not provided much data regarding the building wall and foundation details so it is not possible to provide much help on how to best locate and secure the frost resistant type of faucet. It is a pretty good guess that the quick hack job installation of the existing faucet through the crawl space vents was done that way because it was the easiest way to poke through the wall. When you go to modify the installation it would be good to locate the frost resistant type unit away from the vents. (In fact the vents may want to be insulated during freezing weather). It is common to install the external faucet assembly up between the floor joists and out through a hole in the rim joist. This places the pipe assembly up close to the floor where the heated interior of the building keeps the area warmer.