That was a defensive/go away bite because you touched her unexpectedly. She did not associate you opening her enclosure with being touched on the side. A hook will help with that, just a light rub on their side to let them know that it's "you" about to fool with them, and if the boa strikes the hook you don't care.
You can also use the hook to control their head, but that's usually when they are foody. A light touch or rub under the chin or on the side of the neck lets them know it's not feeding time.