agressive 9 week old female!

Question
Hello- We recently added 2 beautiful yellow lab pups to  our family.  We let the children choose and came home with both the runt and the largest females in the litter!  Odd combo, but both very sweet pups.  The runt, Sophie actually seems to dominate Lily (who is almost 4 pounds heavier).  However, she is EXTREMELY submissive and docile with both the children and our 12 year old female black lab.  She really is (so far) the definition of a lab temperament.  Lily on the other hand is VERY stubborn.  

So here's my big concern.  Recently Lily has both growled and snapped at the children and myself..never my husband when we have tried to remove her from something she is destroying or take her out to potty.  When she snapped at my 7 year old I instinctively got defensive (for fear she will continue and at her present pace she is going to be a BIG dog).  I grabbed her muzzle closed tight and pushed her to the floor while saying "no" very sternly.  She actually did not back down.  She continued to fight me and growl.  It took four times of this type of domination to get her to a point I could pick her up to love and cuddle her.  I am at a complete loss.  We have had many dogs and never at this young of an age did they exhibit this persistent aggressiveness.  I actually feel bad about the way I handled it...she is very young, should I have tried to show this type of dominance?  PLEASE offer your advice on how to deal/ correct this behavior.  

Thanks so much!
Stephanie

Answer
With somebody the right age in the family, 4-H dog training is a great idea.
In my area, clubs form soon after the first of the year.  Even many urban
areas have 4-H.  For info look in your phone book under government listings
for extension or cooperative extension offices.  Ask specifically about a dog
or canine club.  The dogs see all the people and dogs in the household as a
pack with each having their own rank in the pack and a top dog.  Life is much
easier if the 2 legged pack members outrank the 4 legged ones.  You can learn
to play the role of top dog by reading some books or going to a good obedience
class.  A good obedience class or book is about you being top dog, not about rewarding standard commands a treat. Start at http://www.dogsbestfriend.com/  Here are some gentle ways of letting a young puppy know who is top dog:

''Elevation for small puppies:  Sit on the floor and gently put your hands around your pup's middle, below his front legs, and lift him up.  He is facing you.  Hold him for 15 seconds.  Repeat until he no longer struggles.  If he is past 10-12 weeks, lift his front feet off the ground, but don't pick him up.  

Cradling for small puppies:  Hold your puppy gently on his back, as you would cradle a small baby.  If he struggles, hold him firmly until he quiets for 10-15 seconds.  With larger pups, you can do this as your sit on the floor, with your pup between your legs.

Quiet lying down:  Place your pup on the floor on his side, with all 4 legs pointing away from you.  Use your hands on his neck/shoulder area and middle, to hold him in this position.  When he is quiet, praise him.  Lengthen the time that you keep him quietly in this position.  When he accepts this position well, handle his paws and muzzle, while keeping him quiet.''

The quotes mean this isn't my original work.  It is copied from my Puppy Raising Manual.  I have long used these or minor variations of them, and they are very effective.  You may want to give him a belly rub while he is on his back too.  Helps bonding.  There is a big difference between him rolling over and demanding a belly rub, and you choosing a time to roll him over and rub his belly.  The latter cements your place as pack leader.