Well, it took me far longer than it should have, but I finally got all the evidence of the art gallery off the wall. All that is possible at least. I am mow missing some wall paint and have the added feature of slightly yellowed and reddened areas where the finger paint was the thickest. The parts that look tannish are the parts that are now missing wall paint.
As show here, the construction paper did not fully remove when pulled off the wall. There were quire a few pieces left that were bound to the finger paint.
The finger paint reacted weird (or maybe as expected; I'm no scientist) with the wall paint in some places and peeled off as I was removing the finger paint. I was correct when I remembered that I bought washable finger paint, but apparently when you combine it with construction paper and wall paint it becomes "almost washable" finger paint.
I am still unhappy about this, but at least she picked a wall that I hadn't already painted. I really might have strangled her then.