I think you are doing fine. You are in an ebb and flow period with her, and if you keep working on it she's going to get it and do just fine.
Stay consistent. If you ask for a sit, she sits, even if you help her. Tell her she's a good girl when she's sitting and if you are consistent - she will learn that you mean it (say it only once, then make it happen) and won't test you so much. Your timing will get better and you can ask for that sit before she lunges at another dog. (Reaction to another dog - meet and greet, also Friendly stranger test)
Coming when called needs a lot of work. Start indoors, toss a treat a few feet away from you and she will go eat it - as soon as she is reaching for the treat, call her come (show her you have another cookie!) and when she gets to you, give her that cookie. Repeat a couple times and end on a good note. (yes, you want her to eat the cookie you've tossed, but not to linger over it while she chews 30 times and blows off your come command) I think this also introduces what will later be a part of the retrieve (come back quickly) so I start saying "get it" when I throw the treat... just thought of another tip, use a light colored treat that will really stand out against the flooring ie, one that she can see. I use bright orange cheese balls, or white cheese/chicken chunks.
You might leave a light line attached to her so you can reinforce the come command if she wants to leave... another tip, do this before her meal when she is hungry. Also, put your other pets in another room so they can't interrupt. Play the game in the driveway (on leash please) and in the safety of your fenced yard. Call her to come whenever something good will happen. Do yourself a favor and always touch her collar too - when giving the other cookie. So many shelties I see want to play "keep away from my collar"
I wish you much success with your dog, you are doing so well and you two are going to pass and succeed with the CGC and beyond. I am an evaluator and if you are not quite ready, keep training and take the test again when you feel you are ready!
If you need some specific hints or helps, I'll be happy to help in any way I can.
We didn't talk about stays, how is she with that?