Feral Cat -- Problem

we have a feral cat that lives with us.  i got her about 5 years ago when she was itty bitty and meowing underneath the floor.  i didn't move her at first because i kept thinking the mother would come back, but i finally gave up on mom.  i got her to come out by offering food but it was still a challenge to get ahold of her.  she hissed and spat and clawed and hissed and spat.  i have only once been able to get her to the vet.  i tell this part because we're moving! and she needs to move with us! and i cannot get her to take her to the new house.  very frustrating.  i'm not leaving her here either.  so today i called the vet and explained the problem and he said he'd give me a tranquilizer for her.  that'll be great.  i'll go get it first thing tomorrow.  i sure hope it's a put-her-OUT tranquilizer, not just anti-anxiety.  she needs to be flat out on the floor if she's gonna get moved to yadkin county.  she is a beautiful tortoiseshell cat, gorgeous colorings of black and gold.  i hope everything works out for her tomorrow.