RE GEL However changing your reaction to her negativity...that you DO have control over, stop listening to it.....Remove yourself from the situation for awhile, go do something else
Cave time, working at the customer's site instead of bringing them back to the shop. I do that.

Don't tell her how to fix it so she doesn't come across that way, she needs to figure that out (which BTW she won't do, as long as she has you for her sounding board.)
Got that and see where trying to be helpful wasn't working. I am seeing some examples that Schnarch did with the biracial couple W was advised to do, to not rescue her H is OK and preferable.

it's that kind of honesty and owning my own reactions/behaviors....and NOT rescuing my H from his reactions/behaviors that has helped us the most.
I am happy to hear it is working for you. I try to take my advice from someone that has had successes and has been in the trenches.

Lou