Some great points made about feral cats, Linda!
If the vets will do it, a house call would be better than a car ride and a strange place. No matter how cozy and nice it seems to you, Zoey is unlikely to feel the same way about it! Maybe a friend can take your dogs for a walk or distract them in another room while the cat is being treated.
Flower essences would definitely help her adjust to the needles and everything else about the situation. Rescue Remedy, which you can get at most health food stores, would be totally appropriate in this case. I'd start putting it in her food or water now, then give an extra dose the night before, morning of, and before the appointment--and keep it on you in case she needs it at any time during treatment. You can just put a couple of drops in your hand and rub her around the head, ears, or paws, so you won't be getting in the way of the acupuncture.