Competition obedience does require precision and, honestly, I would prefer that the critiquing begin as I'm learning something so I don't spend all my time and energy learning something that I'll have to relearn correctly later but that's me. Other people may have different opinions. That being said there are "levels" of precision. If you want top scores, you are going to have to be extremely precise. If a Q is all you are looking for, you can be less precise. Remember that if your dog always sits slightly crooked in practice, it will be greatly magnified in the ring. All the errors are magnified because of the stress of the dog and handler, and the new location/people/sights/sounds, etc
It sounds like you don't really like this class or instructor so rather than stress about it, why don't you find someone who's style meshes better with your own? I can't imagine it would be a lot of fun if you feel you aren't liked or always picked on by this instructor. Obedience is supposed to be fun! You are there spending time with your best buddy. What could be more fun?
Don't worry that it is you! I would find a new class, or one that is more geared to what YOU want out of Emilu. Does it matter to you that your feet are turned outwardly?
Maybe take the rest of the summer off and give Em a break, and yourself, and head back in thinking 'THIS IS FOR ME AND MY DOG' and not that maybe one day you will be in a ring somewhere. It takes a lot of the edge off if you don't really care.
Also, I recommend getting your MEAN voice out when she doesn't come on first command. This is THE MOST IMPORTANT command they should know. I want a dog so eagre to get back to me that they nearly fall over. If she isn't about food, try toys, or turn and run as fast as you can from her. That will scare the crap out of her. But it is very important that they understand this.