oof, that’s tough. you have a lot of work ahead of you.
first: please report this person. they’re breaking the law by selling puppies under 8 weeks of age. they’ve done you no favors by selling you a puppy that is lacking in ALL socialization with littermates.
second: at this point, i believe puppies should be eating a gruel made with puppy milk and puppy-specific kibble. http://www.dogbreedinfo.com/whelpingphotos4.htm
Hello Cheryl….you would need to consult a Vet to find out why one side of her jaw is firmer on one side than the other. It could be an infection, it could be congenitial or something else entirely. I would get her checked over by a Vet as soon as you can.