There could be several causes to this problem or a combination of them;
This could potentially be due to nerves. When a puppy is first taken away from its mother into a new home it can be very traumatic for the puppy. When I first got my dog Lucky as a puppy she was very anxious, especially the initial night. First night she was away from her mother. She was sleeping with me in my bed and was panting very heavily. Now, she didn't have loose bowels, however loose bowels is another sign of anxiety or nerves. This may sound a little gross, but sometimes when I am very anxious or nervous I occasionally get loose bowels. It has to do with the brain-gut function. The two are directly linked. Nerves and anxiety also cause the panting and could cause skittishness. If this may be the case, just do whatever you can to keep her comfortable. This will clear up with time if this is the issue. Within a week or less she should be well adjusted to you and her new living environment and should be just fine. Here are some natural remedies you may wish to try though for the time being that may help her calm down and reduce anxiety;
Dog Anxiety Natural Remedies | Herbs and Homeopathy for Anxiety in Dogs
The second cause of this or adding to it could be change in diet. What type of food are you feeding her now and what type of food was she eating before you got her? If you don't slowly transition a puppy from one food to another when switching brands it generally causes loose bowels and general gastro-upset. You should slowly mix the food she was on before you got her with her new food, gradually adding a bit more and more of the new food over the course of 1 week until she's on the new food. This will be a lot easier on her system.
The third potential cause of amplification agent in this case could be worms. Many, many puppies have worms. My dog did for one when I first got her. Worms can cause loose bowels. When she goes, take a look at it or poke it a bit (gross I know lol) and see if you can see any little worms in there. Lucky's looked like little white pieces of rice. Even if you don't see any she could still have worms. There are all different types of worms and some can't be detected by the naked eye. Have you scheduled a vet appointment yet for the pup? If not, go ahead and do that and have her checked for worms as every puppy should. If she does have worms your vet will probably supply you with a deworming medication to give your dog. Ig you're the type of person who would prefer trying to deworm your dog naturally rather than risk adverse effects from commercial deworming medication, here's a link about natural deworming;
Home Remedy for Worming Dogs
Best Way - Natural Dewormers for Dogs | eHow.com
If you do decide to go the natural approach make sure to have the dog rechecked after naturally treating the worms to assure they've gone away.
For the loose bowel make sure the dog has plenty of fresh water at all times to eliminate the chance of dehydration. You can also add some canned pumpkin (not pie filler) to the food to firm stool.
Good Luck!