OK, sorry but I need some clarification.
You say after 20 hours of the sequestrant, slowly bring the Cl up. To what? This pool's clearly in need of a shock being a bit murky. I'm of the understanding that any Cl less than shock level at this point would be pointless. Is this just a test to see if there's residual Cu left?

Also, is the water swimmable during this?
Thanks.

(also, I'm advising her long-distance, so the simpler the better)