So in retrospect, I believe it was my fault that Teresa was frustrated - and I was frustrated. She was, "under the hood" with the bucking bar, making shop heads and I was on the outside with the rivet gun. So she had to buck and then check each rivet. It was a little harder to get on these rivets as the nearby rib is at an angle. I figured we should go back to school (or actually "go to school" for the first time). I kinda just threw her in with the bucking bar - as most of the other rivets she bucked were of the backrivet variety.
So, this morning, I pulled out some scrap skins and drilled some 3/32" holes in them, then deburred and dimpled them to have Teresa get some non-pressure practice in. We simulated some under-driven rivets that we could "finish" - and we also simulated some over-driven rivets. She got more work with the rivet gauge and practice always helps. After that, she was ready to get going for real. I think it helped.
This is post-practice - with a few rivets done, underdone and overdone on purpose