Just a note on the prong collar, please have someone show you how to properly use it;
1.] where to attach the lead [at the swivel ring not the other ring] 2.] how to break it apart to adjust the links to properly fit and what is a proper fit
3.] how to put it the dog and for storage when off the dog.
I also would suggest using gloves when working Liberty, especially if your going to use longer leads, they can slip through your hands without gloves and burn your skin. Remember dogs can become 'line/lead' smart and 'collar' smart... that is they will learn to perform correctly while on a lead or long line or with a training type collar, but know when they are not. It is all about pack leader, which Liberty is. Just hangin out with her at this point just enforces her behavior... unfortunately she doesn't think like us humans... it would be so much easier if she did, huh?
Can your Dad help you in working with Liberty everyday? Labs can be a handful until well after 2 years old under the best of circumstances. I'm not comfortable in saying that masking the problem with tranquilizers is the answer, the problem still remains. I don't think Liberty is a 'bad' dog at all, she is just out of control because she as no real solid training from her humans.
$20 dollars to friends? $150 elsewhere? No wonder the breeder has such a problem with his pups! He shouldn't be breeding Labradors.
Unfortunately, the best and last advise I can give is you may need to have a serious talk with all concerned, including yourself, as to what you feel you may be actually able to achieve in Liberty's re-training.