Just to add a bit more weight to both Ghilly's excellent reply and to what Whitroze has said ... yes, vet now, not later. Get this little girl checked over. I'm hoping it's nothing more than the psychological trauma of the puppy farm and she's just in slow recovery from it, but it could also be a physical problem, or both for that matter. Many dogs from these dreadful places do have lots of issues, many of which can be sorted out over time with lots of love and affection ... and patience ... but the tongue smacking sounds more of a physical symptom that needs professional attention to diagnose any problems. Good luck. Please let us know how you get on. Tony
I agree with Ghilly that there could be just about anything since she was rescued from a puppy mill and those places tend to care more about making money than proper care of the pets.
The tongue smacking and odd expression and behavior is a concern. This very well could be a dental issue or stomach upset. Another concern with this behavior is the possibility of a low grade seizure. (not all seizures have noticable "shaking") If your dog is not doing this constantly, then it would be a great idea to write down when she does it and for how long.
A vet visit is probably a good idea so the problem can be found and treated. Please keep us updated if you can.
Puppy mills traditionally do not take care of their dogs, so there is a chance that anything could be the problem here. It might be psychological and it might be physiological. I would hope that, rescuing her from such a bad situation, you took her to the vet right away to make sure she was healthy, or at least in order to know what you would possibly be dealing with down the road. If you didn't take her to the vet when you got her, you probably need to take her now because the symptoms that you list tell me that she doesn't feel well and is trying to get off by herself for some reason. The tongue thing could mean that she has a toothache or it could also mean that she is nauseous. She needs an examination by a vet so that he can actually look into her mouth and give her a good going-over to make sure of what the problem, if there is one, is. Please post back and let us know what the vet says.
Ghilly