I think it is completely normal as well Paige has just started to bark and she is 10 weeks old so hopefully she won't be a very vocal Chihuahua. They say there is two kinds of Chihuahua's when it comes to them barking, there is either a very quiet dog that only barks when it is completely necassary and then there is the kind thta barks about everything, if your Phoebe is already barking and she is just 6 and a half weeks you may have gotten your hands on a noisy one!!!
I always like to watch puppies play real rowdy with all the barking and growling, I think it is normal as long as you can pet her in the middle of her playing and her tail starts to wag, if she goes after your hand then that is something that, In my opinion can be worked with.
~Angela and the group~
Oscar~ Male Crested Gecko
Burt~ Male Leopard Gecko
Ernie~ Male Leopard Gecko
Candy~ Female Ball Python
Gidget~ Female Leopard Gecko
Paige~ Female Cholcolate Chihuahua
Marley~ Female Harlequin Great Dane