What happens if you open the door to the whelping area, let her out, and close the door, take her to the kitchen and give her food or whatever, and then crate her while you clean the box, weight the puppies, etc.
All my bitches do not show any aggression with me around the puppies from newborn on up. But some of them show displeasure with other people coming around. They aren't aggressive, but you can see that some do not feel comfortable, and wish the people would leave -- this behavior is strong in the first couple of weeks. Approaching six or seven weeks it reduces dramatically. Like the bitch knows the pups do not need as much protection.
I am guessing we really don't know much about the beagle's past. Being raised as a single pet, or a pet in a family of one or two dogs, is a lot different than running with a pack of dogs in a near-feral situation -- 13 dogs in a back yard.
The pregnant bitch, and new dam that lives in this kind of situation, is going to, by necessity, become a bitch to the other dogs and any humans that come on the scene. She is near feral, and her maternal instincts are strong. She has been building up to ward off anything and anyone that might harm her puppies. You're it.
The thing is, at 4 days, it isn't an issue because the puppies do not become imprinted on their mother until they start noticing other puppies -- eyes open and able to focus, ears open, etc. 2 and more likely 3 weeks old. But at that time, witnessing their dam express aggression at normal situations can be very bad for the puppies. A bitch in a feral situation my have acquired a behavior that never would have been this bad if she was in a home and love by/bonded with her owner. I don't know that it is genetic. Nature vs. Nurture.
I would COMPLETELY remove any possibility of other dogs or children being anywhere near her and her puppies. Reduce the stress level for her ALL THE TIME. When you need to do something with the area and puppies, crate her if possible. She may be more stressed outside the room, than in the room. Or less. Talk to her. Tell her you will give them back in a few minutes, just changing the box.
At the same time, don't let her be a jerk to you. When she tries to drive you away with teeth, you tell her Eh! No!. Her old life is over, her new life has begun, and we can't let bad habits set in, even though she is a new mother. If at all possible avoid conflict by crating her, or taking her out of the area where you need to be with the puppies, avoiding the conflict prior to problems. Keep time away from the puppies to a minimum. ASAP, open the crate and tell her to go back to her puppies. Right now the puppies need a good mother more than they need you. If the aggression toward you does not reduce over the next 2 weeks, you might have to rethink how long you are going to keep the bitch with the puppies, and how you are going to separate her when you have strangers come over for socialization.
Heidi Ho, Odie
Joy-Joy, Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.