Definately take her to Obedience! My Border Collie has been through ongoing Obedience classes since we got him, when he was 8 months old and not trained at all, he wasn't even leash trained. We have been through four levels of Obedience, up to the competitive level, and he has loved it. It's really a good bonding experience for you and your dog, and it'll teach you how to handle her and your other dogs. Just make sure you look at all the available classes, and only go to POSITIVE REINFORCEMENT based training. That is the only way to go with BC's, as they are highly sensitive and do not do well with harsh corrections. I once made the mistake of going to a Petco training class when I first got Gonzo, where they practiced kneeing, lots of collar grabbing, and really harsh corrections, and he would completely shut down. Make sure you are patient and supportive with her, and give her TONS of treats and praise through the whole process. Find the best trainer possible, and ask for references from your vet or other dog owners... Just make sure you find training that is gentle and positive, and isn't a total ripoff (as some places definately are). Good luck!

Oh, and, good job for taking the girl into your home! All dogs, BC's especially, crave to be inside with their people and do not do well being tied up outside their entire life. Being tied up like that might have caused some of the behavior problems you see in her... it can do a lot of damage to a dog