How big was the "bag" of baking soda? What was she hoping to do by adding it? The baking soda will raise alkalinity but you say alkalinity was OK. If she was trying to raise pH then she should have used Borax. Without knowing what the original pH is it would be hard to guess how much to use.

If you can post some test numbers that would likely help get you some suggestions but "bag" to me sounds like a lot (25 lbs?) so I have a feeling that the alkalinity is now through the roof. I don't know what would happen in that case but I'm sure someone else here would.

Peter