@Pampered chicken girl
To make the transition to off-leash work, get a 20-foot length of clothesline and put a buckle snap at one end. Be SURE it can't come loose. Attach it to her training collar along with your six-foot leash and run through your training routine in a busy environment with plenty of distractions (no cats, we don't want one to grab the end of the clothesline and play with it!). Let the clothesline drag along behind you. Work her until she ignores it. If she steps on it just keep going.
After ten minutes or so, do a Sit, reach down to pet her, and casually unhook the leash. Throw the leash over your shoulder, give a Heel command and move forward. If she's ready for off-leash work she should Heel as always. Continue your training routine. If anything distracts her and she starts to charge, STEP ON THE CLOTHESLINE. Do not attempt to grab it with your hand until after you have stepped on it. For one thing, she's faster than you and you could miss. For another, if you grab it while she's going at speed you could get a nasty rope burn.
Chances are she will Heel beautifully. But if you find yourself having to make corrections, go home, you're done for the day. Take about a foot ling piece of clothesline and make yourself what's called a "tab." It's basically a length of rope, folded in half and tied in an overhand knot at one end. Then push the folded end through the ring in the training collar and thread the knot back through the loop, to form a very short leash, or handle hanging from her collar. I'll post a pic tomorrow. You'll grab the knot if you need to make a correction.
Tomorrow, repeat, only now if you need to give an off-leash correction, you have this little rope handle you can grab.
Every day repeat this exercise: start out on leash, remove the leash, let her drag the clothesline. Only make this change: every day, cut a foot or two off the end of the clothesline.
In a week or two you will realize you couldn't step on that clothesline if your life depended on it. And you'll also realize - you don't need to. You and your dog have gradually built confidence in each other. It's time to get rid of the clothesline. And you decide when you don't need the tab any more.
Congratulations. Your dog is now Heeling Free!