I have a 4.5 month bassett. She is starting to nip at people especially in the evening. She nips at their ankles and even though we turn her over onto her back etc. it still occurs and she has now drawn blood twice (not seriously) on my two grown up daughters who have come to visit.
Nipping and biting is very normal puppy behavior. It's usually an attention-seeking behavior, but it can sometimes be an attempt at dominance. It tends to be most apparent during the early months, gradually decreasing after teething ends (at about 6 months old). BUT it is important to discourage this habit early and firmly.
Generally a verbal correction and a withdrawal of attention is enough to make the pup realize that this in undesirable behavior. However, some puppies are more stubborn about it than others and may need other types of correction - such as the water-spray bottle. You can read about the different ways of dealing with this behavior on my Puppy Biting page.
I wouldn't recommend rolling her over onto her back, that's also called the 'alpha roll', as it is more likely to cause the behavior to escalate than it is to correct it. Also, never physically punish a puppy for nipping, or shout or raise your voice. All of those are counter-productive. I think you'll find the methods on the page mentioned above will take care of it for you.
Best of luck with your pup.