It seems to me that your little girl may just be lonely for other dog companionship...
When dogs socialize and play together, they grab each other by the neck, ears, legs, etc. and wrestle around a lot. Mounting is also a part of play used to establish and confirm dominance.
***Females display these play behaviors just as often as males.***
Your puppy is playing with her bed most likely because it is the nearest thing she has to another dog (it smells like a dog!) to play with.
In the absense of other behaviors, I do believe that she is both Healthy and Normal! If there is not a good place for you to let her play with other dogs of her age and size, then do get her a variety of other large stuffed toys to play with (she obviously likes the size of her bed for this purpose).
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