Unless she is shooting a traditional single action and is using the hammer as the firing mechanism..... This way they keep the trigger down, pull back the hammer and when you release the hammer the gun fires.
Like many sports they have different techniques to get an edge. The "ammo" they are shooting is black powder with a cardboard cap to keep it in.
I am not sure if that technique is allowed in this sport. Cowboy action shooting does a similar thing with traditional pump action shotguns by holding the trigger.