Our JRT attacks feet

Question
We have a female purebred JRT that is 8 mos old (Holly).  We have had her for 5 mos.  Our problem is in the past month or so, she has started tugging and biting at our 8 year old daughter's feet.  Anytime my daughter (Maggie) takes Holly out to potty or play or even just for a walk, Holly gets aggressive and bites Maggie's shoes and ankles until she pulls her shoes completely off her feet.  When this happens, Maggie is so frightened because Holly is growling viciously and Maggie has actually been bitten a few times on the ankles and shins.  Holly does not do this to me or my husband nor will she do this when Maggie is barefoot.  We have to physically drag Holly off of Maggie and it's usually with one of Maggie's shoes in her mouth.
We have tried saying "No!", but usually Holly pays no mind because she is in a frenzy.  I hate to admit it, but one time she had Maggie's ankle in such a grip that I instinctively went into attack mode myself and struck the dog to get her off.  I know that was the wrong thing to do.   She is definately trainable because she knows sit, stay, come, lay down, shake.  She is otherwise friendly.  She naps with Maggie on the couch and plays nice most of the time.  We just don't know where this is coming from or what to do.  Please help.

Answer
Hi Leslie,
Because Maggie is so young, Holly is viewing her as her "equal" or playmate and simply doing what playmates do.... play!! BUT, humans aren't puppies and those little razor teeth hurt!! You'll have to teach Maggie how to correct Holly, which is sometimes easier said than done, but it is definitely do-able with some patience and consistency.  
First don't let Holly be off-leash when playing with Maggie; have the leash always available for correction. Teach Maggie to loudly say "NO" just like you do, and to STOP walking or running the second she starts biting at her feet. Teach her to step up high on the leash near the collar to trap Holly's head near the ground and keep it immobile. If she (Maggie) runs, screams or kicks, Holly will think it's a game and get into that frenzied state of mind. Also, I don't blame you for getting angry at Holly, of course as mothers our first instinct is to protect our child!
After Maggie has stopped moving and is standing still, teach her to bend down and with her hand firmly grip or "bite" the back of Holly's neck and push her away and say NO!!! - She might have to stand there for 10 minutes while the dog keeps trying to get at her feet - it takes puppies TIME to learn new behaviors and corrections, and repetition is the best teacher. She'll have to do it over and over and over again until Holly figures out that this game isn't very much fun anymore. If it's too hard for Maggie to step on the leash, have her pull it UP at the same time she is yelling "NO". I realize this is a lot for an 8 year old to do so you'll have to help her to learn how to do it.  The best thing is for her NOT to get nervous or hysterical but stop dead in her tracks, be a very serious 8 year old and refuse to play the "game". The "bite" or grab on Holly's neck is supposed to simulate a "mother dog" teaching and redirecting the puppy's state of mind. Dogs don't use language to correct their puppies, so this technique as well as the human "NO"! sends a clear message.

So, The puppy starts biting her ankles....
   Maggie steps on the leash (or yanks it up)
   Maggie bends down, "bites" the pup on the neck, says NO BITE
   and at the same time, pushes Holly away from her feet
   Maggie stands still and refuses to play
   Puppy WILL learn!

As with all youngsters, it will take some time so have patience and stay consistent.
BEST OF LUCK!! You can do it!
Write anytime,
Carol