It's a shame you have a pup from a puppy farm, but it's good that you seem determined to do your best for her.
She will need all the help you can give her, especially over the next few weeks... as Jane S says, definately get her seen by the vets, who should advise you on all aspects of health (worming, vaccinations etc). Puppies normally learn a lot during the few weeks they have with their litter mates, and you will need to help her learn these things in other ways. Once she is vaccinated, make sure she mixes with lots of nice friendly dogs, as she may be lacking in methods of doggie communication. In the meantime she is still very young - she will need lots of sleep... I would try and set up her box so she can use it during the day too, as she will feel safe and secure there... It sounds like she is doing really well overnight. Over the next few weeks, gradually introduce her to new experiences, like going outside (if there is a secure area not visited by other dogs, she can be on the ground, if not you will have to carry her until she has had all her vaccinations), household noises (if she was puppy farm bred, she'll probably not have experienced things like a vacuum cleaner), different people, noises etc - but don't overwhelm her, especially in the first couple of weeks.
You will probably have more difficulty managing her puppy biting and chewing as she gets older, as she will not have learned her early lesson from her mum and siblings... there is a lot of advice on here about puppy biting and if you follow it you will get there, but it might take longer than for people who's pups come to them at 8 weeks... I'm sure you will be patient and kind with her (but do know most of us have been driven to despair by our pups at one point or another).
Are you able to attend any good training classes with her?? Obviously this will be several weeks away, but training classes (that use positive training methods) and any attached socialisation groups will also help your pup overcome her start in life.
I don't know anything about the nutritional needs of such a young pup, but hopefully someone on here who breeds will have more advice for you. Likewise with bathing.
She is gorgeous
and it sounds like you are determined to do everything right for her - this is a great place for advice on all aspects of cocker spaniels... It sounds like she is a very confident little girl, and hopefully this will help her and you in the long run.
