I honestly have no idea how you can fix things for Beth. I mean, as soon as I realized that I was backing Jia Li into a corner with her a-social behavior, I changed her a bit to better fit something that would be playable.
I wish I knew how to help you fix Beth, but I haven't the slightest clue. If you really like this board, and you don't want to quit, you could always drop Beth in favor of a different kind of character if you don't feel like you have other alternatives for her. =\