That is the down side of w/c colubrids. My friend has a garter and he swings what ever part of his body is not in your hands around and around in circles...while musking of course
It could be worse, could have been a w/c female watersnake, they thrash and bite the hell out of you
Oh, and be sure to get the snake dewormed as soon as it settles down a little, parasites are the #1 killer of w/c rough greens.
She might just be freaked out from the long ride in the mail. Give her a week or two...