What has been stated previously couldn't be more right. At six weeks old, she should still be with her siblings and mother.
Unfortunately, you're really going to have to work hard with her to get her to train correctly because of how early she left her litter. It's important that puppies are with their siblings until eight weeks of age, seven at the very least. At eight weeks, they begin to learn to socialize, which is a crucial aspect of puppyhood and will effect the puppy's behavior for the future. By taking her away from that, she doesn't understand that biting a living creature is painful, etc.
Because she is so young, I would suggest puppy-pad training. She's still too little to be learning to go outside or even be crate trained really.
Edit: Also, it's normal for puppies to be weary of the lead for a while. My puppy is 10 weeks old and he still doesn't understand the concept of walking on it.
Again, don't expect too much from her at the moment, she is very, very young.