I have had beagles for 20+ years and just added a puppy to our family in
February so your question is certainly fresh on my mind! I would be
surprised if what you are seeing is anything more than typical puppy
mouthiness and growling.
Here are a couple of things to consider. First, puppies get tired really,
really quickly so I bet her mouthiness gets worse after she's been up
playing for 20 minutes or so. I was amazed at how "cranky" Maggie got as
she got tired. I'd try putting your puppy back in the crate if you feel
like the behavior is beginning. Also, I'd be aware of how you react when
she mouths and growls. Sometimes, you can inadvertenly reinforce the
behavior by continuing to "fuss" with the puppy when they do it. Simply get
up and quickly withdraw your attention when it happens. I also gave Maggie
lots of opportunities to chew on toys and I also found that ice cubes were a
great way to divert her biting to something else. Your puppy is still at
the age where she's learning how to appropriately use her mouth. If she
were still in the litter or with adult dogs in your family, they'd also be
helping her to learn what's acceptable.
One of the easiest and most effective training methods you can use to help
with this behavior is to begin hand feeding your puppy her meals. It will
help her learn that your hands are a good thing! And it also begins to
establish that good things come from you and it's worth her efforts to pay
attention to you and focus on you. After you've done that for a couple of
weeks, you can continue to use her meals to begin teaching sit, down, etc.