If you can get someone else to hold her still, use a magnifying glass to see if there are any signs of puncture marks on the skin under her fur. Double puncture-mark, obviously means snake, though in the absence of any other symptoms, I would doubt she has been bitten by a snake, unless it is a non-venomous one.... or signs of a bee sting embedded. Bees leave the sting in, so it does hurt. I know. Because the sting is 'barbed' it's not so easy to just pull out. And doing that can make the inflammation worse.
I have removed my own bee stings, on myself, but wouldn't like to try removing one from a dog, as it can mean a certain amount of 'digging around' which hurts, and has to be done very carefully! I'd let the vet do it.
If she has shown no worse reaction, she'll most likely be OK, and won't have an allergy to the sting, but it is possible infection or an abscess could develop, so it would be best to take her to the vet and get her properly checked.
I hope she's just fine soon!
she does have some swelling at the back of the neck now that I look at it. it is tender also to the touch.
Be on the safe side and take her to the vet. I would do that soon, if she appears to be in pain. It might be wiser not to use Human meds, but to wait for a veterinary prescription. Many human painkillers just aren't a good idea for dogs.
Poor girl. I can't say I know what's wrong here. Are you sure she didn't get stung by a bee or something? Look for any sting marks, bite marks (I'm thinking other critters as well,) or swelling at the back of her neck.
Otherwise, she may possibly have a spinal problem, made suddenly worse, perhaps, by something she did when she was outside?