Why is my kitten meowing?

whenever i hold her in my hands shes constantly meowing... it gets annoying.... we found my dog Peanut gaurding her from our other dog so were not sure how old she is either :/ and Peanut has acted really motherly around her like picking her up in her mouth and taking her under a bed and licks her and snuggles with her... why is a dog doing that to a kitten? why is Snowball (kitten) meowing all the time? and how old is she? THANKS :)