I can't recommend an ecollar...none of the problems you have scream "I need an ecollar!"
You could find a trainer, that might use an ecollar as a tool of his, and then they can show you how to properly use it to fix some of the issues you're having.
In my opinion...you can correct her with a conventional collar when she's barking at the fence. Is she out in the yard by herself when she is barking? If she is, easy fix, don't let her out in the yard by herself. Of course alone she is obedient, she hasn't had enough practice to learn to ignore the other dogs while she's working. You need to take her back to obedience class and keep working with her around other dogs/distractions.