Also, if your yard is fenced in.....do the heel exercise against the fenceline. This gives her boundaries, less escape options, and can focus more on you and the exercise. Remember as well, keep the sessions short. This doesn't mean you can't do them a few times a day though. Say 3-4 sessions, 15 minutes at a time. Maybe 20. Pups have a short attentions span at this age....build her up and ALWAYS end training on a good note with lots of praise. Never end it with frustration or anger. She will sense this. Also, find what motivates her. Either it be a food reward or toy. Always stick with this reward. Keep your corrections firm but not punishing. Training should always be fun. When you are not having fun, stop and take a brake. Be presistant with all your training and corrections. Most of the time when pups/dogs seem not to "get it," it is us humans that are confussing them by our role as leaders. Sit back and take a hard look at how you are training. Look at how you are delivering the corrections and when. Timing plays a role as well.
I think....no, I know people here and/or more classes can avoid the use of a prong